In the presence of a catalyst, at least one isoparaffin having 4 to 6 C atoms per molecule is reacted with at least one olefin having 2 to 6 C atoms per molecule in a liquid phase to obtain a product containing alkylate, a suspension containing isoparaffin and a granular zeolite catalyst being supplied to the upper region of a reaction column. Below the point where the catalyst-containing suspension is supplied, an isoparaffin-olefin mixture is introduced into the reaction column, the temperatures in the reaction column being maintained in the range from 50 to 120.degree. C. From the bottom region of the reaction column a product mixture containing alkylate is withdrawn, and in a separation by distillation alkylate product is recovered therefrom. Preferably, isoparaffin and catalyst are recovered from the separation by distillation and at least partly recirculated to the upper region of the reaction column.