A process for oligomerising alkenes having from 3 to 6 carbon atoms which comprises contacting a feedstock comprising a) one or several alkenes having x carbon atoms, and, b) optionally, one or several alkenes having y carbon atoms, x and y being different, with a catalyst containing a zeolite of the MFS structure type, under conditions to obtain selectively oligomeric product containing predominant amounts of certain oligomers. The process is carried out at a temperature comprised between 125 and 175.degree. C. when the feedstock contains only alkenes with 3 carbon atoms and between 140 and 240.degree. C., preferably between 140 and 200.degree. C. when the feedstock contains comprises at least one alkene with 4 or more carbon atoms.