The present invention provides a process for the preparation of 6-O-methylerythromycin A Form II comprising treating 6-O-methylerythromycin A with organic acid selected form trifluoroacetic acid, para-toluene sulphonic acid, oxalic acid or acetic acid and converting it into an organic salt of 6-O-methylerythromycin A, which can be neutralized by base to give 6-O-methylerythromycin A Form II.