Ni(II)-exchanged amorphous silica-aluminas are effective catalysts for the oligomerization of lower alkenes. The mode of the reaction and the product spectrum obtained depends largely on the reaction temperature employed. At low temperatures (similar to120 degreesC), mainly selective nickel-catalyzed oligomerization is observed (true oligomerization). As the reaction temperature is raised, the formation of hydrocarbons composed of non-integral multiples of the monomer increases (hetero-oligomerization). Plots of the ratio of integral multiples to non-integral multiples of, the monomer versus reaction temperature are powerful indicators of the mode of oligomerization taking place. These plots are described by exponential relationships, and on a logarithmic scale, straight lines are obtained. The catalysts studied by us were grouped into two classes, those of (i) low to medium catalytic activity, and (ii) high catalytic activity. For group (i) catalysts (of relatively low nickel loading), the temperature of 180 degreesC marks the change-over from predominantly hetero-oligomerization. For group (ii) catalysts (high nickel loadings), the contributions of true nickel-catalyzed oligomerization extends further into the high-temperature region (up to similar to300 degreesC). The Y-intercepts of the plots can be taken as a measurement of the intrinsic selectivity of the catalysts (true versus hetero-oligomerization), while the value of the slopes quantifies the sensitivity true to unselective hetero-oligomerization).