Combining ability analysis was done on a diallel cross of a random sample of four different cultivated diploid potato populations (Solanum tuberosum Group Andigena haploid, Gp. Tuberosum haploid, Gp. Phureja and Gp. Stenotomum) to determine the amount of heterosis and the gene action involved in the inheritance of tuber yield, fresh vine yield, total plant accumulation (tuber+vine) fresh and dried, dry vine yield and density (specific gravity). The analyses of variance on data from two locations demonstrated significant general combining ability for most traits, indicating a preponderance of additive gene action. Specific combining ability was not significant for any of the traits. Heritabilities for the more important traits such as tuber yield and density were large enough to ensure progress from selection.