According to the standard economic theory that treats a person as a maximising agent of short run profit, it would be expected that farmers would select round potato varieties with the highest profit potential. However, previous studies treated round potato as one variety and other adoption studies often assumed that profitability was not important in the adoption of improved varieties. Therefore, this study analysed the profitability of round potato and the implications for variety selections by using a sample of 510 farmers drawn from three districts of the Southern Highlands of Tanzania. The main question was whether smallholder round potato farmers considered profit potentials or are there other factors in variety selections? The results showed that Kagiri was the most profitable variety and there were significant differences in profitability among varieties. However, not many farmers produced Kagiri because they used their own criteria in order to make profit. Such criteria included the availability of seed tubers, preferences of the local consumers and processors, common practices, yield, and suitability for home consumption. It was recommended that the role of plant breeders should go beyond the crop characteristics, such as, yield potential, response to inputs, and tolerance to diseases, so as to include both farmers and consumers’ preferences.