diff --git a/align/align.go b/align/align.go
index f644801..6f1d876 100644
--- a/align/align.go
+++ b/align/align.go
@@ -16,6 +16,9 @@ const (
 
 )
 
+var stdaminoacid = []rune{'A', 'R', 'N', 'D', 'C', 'Q', 'E', 'G', 'H', 'I', 'L', 'K', 'M', 'F', 'P', 'S', 'T', 'W', 'Y', 'V'}
+var stdnucleotides = []rune{'A', 'C', 'G', 'T'}
+
 type Alignment interface {
 	AddSequence(name string, sequence string, comment string) error
 	AddSequenceChar(name string, sequence []rune, comment string) error
@@ -34,6 +37,7 @@ type Alignment interface {
 	Recombine(rate float64, lenprop float64)
 	TrimNames(size int) (map[string]string, error)
 	TrimSequences(trimsize int, fromStart bool) error
+	AppendSeqIdentifier(identifier string, right bool)
 	CharStats() map[rune]int64
 	Alphabet() int
 }
@@ -306,6 +310,21 @@ func (a *align) TrimSequences(trimsize int, fromStart bool) error {
 	return nil
 }
 
+// Append a string to all sequence names of the alignment
+// If right is true, then append it to the right of each names,
+// otherwise, appends it to the left
+func (a *align) AppendSeqIdentifier(identifier string, right bool) {
+	if len(identifier) != 0 {
+		for _, seq := range a.seqs {
+			if right {
+				seq.name = seq.name + identifier
+			} else {
+				seq.name = identifier + seq.name
+			}
+		}
+	}
+}
+
 // Samples randomly a subset of the sequences
 // And returns this new alignment
 // If nb < 1 or nb > nbsequences returns nil and an error
@@ -388,3 +407,16 @@ func (a *align) CharStats() map[rune]int64 {
 func (a *align) Alphabet() int {
 	return a.alphabet
 }
+
+func RandomAlignment(alphabet, length, nbseq int) (Alignment, error) {
+	al := NewAlign(alphabet)
+	for i := 0; i < nbseq; i++ {
+		name := fmt.Sprintf("Seq%04d", i)
+		if seq, err := RandomSequence(alphabet, length); err != nil {
+			return nil, err
+		} else {
+			al.AddSequenceChar(name, seq, "")
+		}
+	}
+	return al, nil
+}
diff --git a/align/align_test.go b/align/align_test.go
new file mode 100644
index 0000000..28a6ec8
--- /dev/null
+++ b/align/align_test.go
@@ -0,0 +1,45 @@
+package align
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestRandomAlignment(t *testing.T) {
+	length := 3000
+	nbseqs := 500
+	a, err := RandomAlignment(AMINOACIDS, length, nbseqs)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if a.Length() != length {
+		t.Error(fmt.Sprintf("Length should be %d and is %d", length, a.Length()))
+	}
+	if a.NbSequences() != nbseqs {
+		t.Error(fmt.Sprintf("Nb sequences should be %d and is %d", nbseqs, a.NbSequences()))
+	}
+}
+
+func TestAppendIdentifier(t *testing.T) {
+	a, err := RandomAlignment(AMINOACIDS, 300, 50)
+	if err != nil {
+		t.Error(err)
+
+	}
+	a.AppendSeqIdentifier("IDENT", false)
+
+	a.IterateChar(func(name string, sequence []rune) {
+		if !strings.HasPrefix(name, "IDENT") {
+			t.Error("Sequence name does not start with expected id: IDENT")
+		}
+	})
+
+	a.AppendSeqIdentifier("IDENT", true)
+	a.IterateChar(func(name string, sequence []rune) {
+		if !strings.HasSuffix(name, "IDENT") {
+			t.Error("Sequence name does not end with expected id: IDENT")
+		}
+	})
+}
diff --git a/align/sequence.go b/align/sequence.go
index 777e112..3deaebd 100644
--- a/align/sequence.go
+++ b/align/sequence.go
@@ -1,5 +1,10 @@
 package align
 
+import (
+	"errors"
+	"math/rand"
+)
+
 type Sequence interface {
 	Sequence() string
 	SequenceChar() []rune
@@ -35,3 +40,18 @@ func (s *seq) Name() string {
 func (s *seq) Comment() string {
 	return s.comment
 }
+
+func RandomSequence(alphabet, length int) ([]rune, error) {
+	seq := make([]rune, length)
+	for i := 0; i < length; i++ {
+		switch alphabet {
+		case AMINOACIDS:
+			seq[i] = stdaminoacid[rand.Intn(len(stdaminoacid))]
+		case NUCLEOTIDS:
+			seq[i] = stdnucleotides[rand.Intn(len(stdnucleotides))]
+		default:
+			return nil, errors.New("Unexpected sequence alphabet type")
+		}
+	}
+	return seq, nil
+}
diff --git a/cmd/addid.go b/cmd/addid.go
new file mode 100644
index 0000000..30a8c04
--- /dev/null
+++ b/cmd/addid.go
@@ -0,0 +1,34 @@
+package cmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var addIdOutput string
+var addIdName string
+var addIdRight bool
+
+// addidCmd represents the addid command
+var addidCmd = &cobra.Command{
+	Use:   "addid",
+	Short: "Adds a string to each sequence identifier of the input alignment",
+	Long: `Adds a string to each sequence identifier of the input alignment.
+
+The string may be added to the left or to the right of each sequence identifier.
+`,
+	Run: func(cmd *cobra.Command, args []string) {
+		f := openWriteFile(addIdOutput)
+		for al := range rootaligns {
+			al.AppendSeqIdentifier(addIdName, addIdRight)
+			writeAlign(al, f)
+		}
+		f.Close()
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(addidCmd)
+	addidCmd.PersistentFlags().StringVarP(&addIdOutput, "out-align", "o", "stdout", "Renamed alignment output file")
+	addidCmd.PersistentFlags().StringVarP(&addIdName, "name", "n", "none", "String to add to sequence names")
+	addidCmd.PersistentFlags().BoolVarP(&addIdRight, "right", "r", false, "Adds the String on the right of sequence names (otherwise, adds to left)")
+}
diff --git a/cmd/random.go b/cmd/random.go
new file mode 100644
index 0000000..dba2bdd
--- /dev/null
+++ b/cmd/random.go
@@ -0,0 +1,53 @@
+package cmd
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/fredericlemoine/goalign/align"
+	"github.com/fredericlemoine/goalign/io"
+	"github.com/spf13/cobra"
+)
+
+var randomLength, randomSize int
+var randomAA bool
+var randomOutput string
+var randomSeed int64
+
+// randomCmd represents the random command
+var randomCmd = &cobra.Command{
+	Use:   "random",
+	Short: "Generate random sequences",
+	Long: `Generate random sequences.
+`,
+	PersistentPreRun: func(cmd *cobra.Command, args []string) {
+	},
+	Run: func(cmd *cobra.Command, args []string) {
+		rand.Seed(sampleSeed)
+		var a align.Alignment
+		var err error
+		f := openWriteFile(addIdOutput)
+		if !randomAA {
+			a, err = align.RandomAlignment(align.NUCLEOTIDS, randomLength, randomSize)
+			if err != nil {
+				io.ExitWithMessage(err)
+			}
+		} else {
+			a, err = align.RandomAlignment(align.AMINOACIDS, randomLength, randomSize)
+			if err != nil {
+				io.ExitWithMessage(err)
+			}
+		}
+		writeAlign(a, f)
+		f.Close()
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(randomCmd)
+	randomCmd.PersistentFlags().IntVarP(&randomLength, "length", "l", 100, "Length of sequences to generate")
+	randomCmd.PersistentFlags().IntVarP(&randomSize, "nb-seqs", "n", 10, "Number of sequences to generate")
+	randomCmd.PersistentFlags().BoolVarP(&randomAA, "amino-acids", "a", false, "Aminoacid sequences (otherwise, nucleotides)")
+	randomCmd.PersistentFlags().StringVarP(&randomOutput, "out-align", "o", "stdout", "Random alignment output file")
+	randomCmd.PersistentFlags().Int64VarP(&randomSeed, "seed", "s", time.Now().UTC().UnixNano(), "Initial Random Seed")
+}