It is provided a process for the preparation of bimatoprost, which comprises: a) reacting a compound of formula (III) with ethylamine in the presence of a suitable solvent; and b) deprotecting compound obtained in step a) to obtain bimatoprost, wherein R1 is selected from (C1-C16)alkyl, (C1C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl, —(CH2—CH2—O)n—CH3 wherein n=1, 2, 3 or 4, and —CH(O—CH2—CH2)2; R2 is selected from H, (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(CrC16)alkyl, aryl, (C1-C16)alkylaryl, allyl; or, alternatively, R1 and R2 taken together are selected from —CH2—CH2—CH2—, —CH2—CH2—, —O—CH2—CH2—, and —O—CH═CH—. There are also provided intermediates useful in such preparation process.