Abstract: A process for preparing alkylbenzenes, which comprises alkylation of benzene or alkylderivatives thereof with olefines in the presence of a catalyst comprising a product prepared by reacting metallic aluminum with a chlorinated hydrocarbon in a medium of benzene or an alkylbenzene at a weight ratio between metallic aluminum and said chlorinated hydrocarbon ranging from 1:0.08 to 1:17 respectively; said alkylation being conducted at a temperature within the range of from 50.degree. to 180.degree. C. under a pressure within the range of from 2 to 20 atm. The catalyst employed in the process according to the present invention is non-hygroscopic; it is prepared by rather simple technology; said catalyst ensures a high yield of the desired products (up to 80-96% as calculated for the reacted olefine) while retaining a high quality thereof (for example, purity degree of ethylbenzene prepared thereon is 99.9179% by weight).