Abstract: A process has been developed for controlling the catalytic co-oligmoerization of 1,3-dienes with Schiff's bases which comprises condensing a 1,3-diene of the formula ##STR1## wherein R.sup.4 and R.sup.5, independently of one another, represent hydrogen or an alkyl group having 1 to 4 carbon atoms with a Schiff base of the formula ##STR2## wherein each of R.sup.1, R.sup.2 and R.sup.3 represents hydrogen alkyl, cycloalkyl, aralkyl, aryl or dimethylamino groups which, in addition, optionally contain functional groups of the group consisting of ethers esters, C.dbd.N double bonds and which can be closed to form a ring, in the presence of a nickel (O)-containing catalyst, and optionally in the presence of an X--H compound with a molar ratio of Ni: X H of from 1:0 to 1:10.