Process for the preparation of abacavir, or its salts or its solvates comprising the step of reacting a compound (IV) where R1 is a (C1-C4)-alkyl radical with anhydrous hydrochloric acid/(C1-C6)-alcohol, and then with tri(C1-C4)-alkyl orthoformate, in the absence of water. The preparation process may include further steps of reacting the compound obtained with cyclopropylamine and subsequently hydrolysis to yield abacavir.