The invention relaters to a process for producing an oligomeric product by oligomerisation of at least one olefinic compound, the process including a) providing an activated oligomerisation catalyst by combining, in any order, i) a source of chromium, ii) a ligating compound of the formula I (R1)mX1(Y) X2 (R2)n. . . . I wherein X1 and X2 are independently an atom selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulphur and selenium or said atom oxidized by S, Se, N or O where the valence of X1 and/or X2 allows for such oxidation, Y is a linking group between X1 and X2, m and n are independently 0, 1 or a larger integer, and R1 and R2 are independently hydrogen, a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group, and R1 being the same or different when m>1, and R2 being the same or different when n>1, iii) a catalyst activator or combination of catalyst activators, b) providing a zinc compound, and c) contacting the at least one olefinic compound with a composition containing the activated oligomerisation catalyst and the zinc compound, the zinc compound being present in a sufficient quantity such that the ratio of the molar amount of zinc in the zinc compound to the molar amount of chromium in the source of chromium is between 1 and 10000 The invention also provides for a process for activating an oligomerisation catalyst to be used to produce an oligomeric product from at least one olefinic compound, as described above