Process for preparing oligomers of alkenes having from 4 to 8 carbon atoms from a feed stream comprising such alkenes or hydrocarbon streams in which such alkenes are present over a nickel-containing, heterogeneous catalyst in n successive adiabatically operated reactors, where n is 2 or an integer greater than 2, at from 30 to 280.degree. C. and pressures of from 1 to 300 bar, where the feed stream has a temperature T.sub.in when it enters the first reaction zone, experiences a temperature increase in each reaction zone and, if this temperature increase is more than T.sub.in+20.degree. C., is brought to a temperature in the range T.sub.in.+-.20.degree. C. before it enters a subsequent reaction zone, wherein the feed stream is divided and the feed substreams obtained in this way are fed to the 2 reactors, or if more than 2 reactors are used to at least 2 of the reactors, with addition of fresh feed in such a way that the temperature in one of the reactors is at most 20.degree. C. higher than that in each of the other reactors used.