- Thiamine pyrophosphate (vitamin B1) is an essential nutrient in the human diet, and is often referred as the energy vitamin. Potato contains modest amounts of thiamine. However, the genetic variation of thiamine concentrations in potato has never been investigated. In this study, we determined thiamine concentrations in freshly-harvested unpeeled tubers of fifty-four potato clones, the majority of them originating from the Pacific Northwest Potato Development Program. Tubers from thirty-nine clones were collected from four different environmental conditions. Thiamine concentrations ranged from 292 to 1317 ng g-1 fresh weight, which gives a good estimate of the genetic variation available in Solanum tuberosum ssp. tuberosum. Thirteen clones/varieties contained >685 ng g-1 fresh weight and four had >800 ng g-1 fresh weight over multiple harvests, indicating that these genotypes would contribute a significant amount of thiamine in the diet (>10% of the Recommended Daily Allowance based on a 175- or 150-g serving, respectively). Broad-sense heritability for thiamine content was calculated as 0.49 with a 95% confidence interval of 0.21–0.72, suggesting that genetic variation accounted for about 50% of the observed variation. There were significant clone and clone x environment effects. After accounting for environmental variation, 25 clones were unstable across environments. Tubers harvested at a mature stage late in the growing season had higher amounts of thiamine than tubers harvested at a young stage early in the season. Storage at cold temperature did not lead to significant thiamine loss; instead, thiamine concentrations slightly increased during storage in some genotypes. These results suggest that increasing the concentration of thiamine in potato is feasible and that all potato varieties may one day be a significant source of thiamine in the human diet.