Abstract: The process for the preparation of pramipexole base and/or its pharmaceutically acceptable salts, especially the hydrochloride salt, in the alkylation reaction of (S)-(?)2,6-diamino-4,5,6,7-tetrahydrobenzothiazole with an alkylating agent, wherein the reaction is carried out in the absence of a base, and in a solvent from which the resulting N-monoalkylated product selectively precipitates out as a salt. After isolation from the reaction mixture, the N-monoalkylated product is converted a) into the free pramipexole base upon treatment with an inorganic base and is then converted into another pharmaceutically acceptable pramipexole salt; or b) directly into another pharmaceutically acceptable pramipexole salt or the hydrate thereof.