The present invention relates to process for the prepatation of Aripiprazole form B having purity at least 99.5% and substantially free from dimer impurity, coprises the steps of ix)dissolving aripiprozle in 25 volume of ethanol with 10% activated carbon x)heating reaction mixture obtain in step(i) to reflux for 5 hrs xi)filtering the reaction mixture obtain in step(ii) stirring the solution obtained in step(iii)for 2-3 hrs at tmperature 20-35c xiii)cooling the solution 0c to 5c for 1 hr xiv)suspending the resutin product obtained in step(v)in water xv)filtrating the resutin product obtained in step(vi) drying at 80 c for 10-12 hrs in hot air to obtain form B having purity at least 99.5%
