Diallel analysis was carried out involving eight diverse varieties of tomato, namely Pusa Early Dwarf, Sl-1, S-12, Punjab Tropics, Sl-120, HS-101, Pusa Ruby and Sl-73-1, to characterize the gene action involved in the inheritance of some of the quantitative traits and to correlate array mean and per se performance with general combining ability (gca) and specific combining ability (sca) effects, respectively.The results indicated that the variance component due to general combining ability was higher than that due to specific combining ability for yield and number of fruits, showing preponderance of an additive type of gene action. On the other hand, all other characters - height, number of branches, locule number, T.S.S., acidity and ascorbic acid content - were found to have a high variance component due to specific combining ability, which means excess of non-additive type gene action. In such cases, heterosis breeding, or any other breeding plan which makes use of specific combining ability effects, would be more effective. High correlation between parental array means and gca effects and between per se performance of the crosses and the sca effects was observed. The implications of the results are discussed.