Potatoes (Solanum tuberosum L.) supplemented with increasing amounts of sodium selenate were analyzed for glycoalkaloid (GA) content. GAs were extracted with 5% acetic acid from freeze-dried tubers of two potato cultivars, Satu and Sini, harvested 10 weeks after planting as immature. The GAs alpha-solanine and alpha-chaconine were quantified by reverse-phase high-performance liquid chromatography (RP-HPLC) with diode array detection. Two independent experiments were performed. In the first experiment, the total GA concentration +/- standard error of the tubers ranged between 105 +/- 9 and 124 +/- 10 mg kg(-1) fresh weight in Satu and between 194 +/- 26 and 228 +/- 10 mg kg(-1) fresh weight in Sini. The ratio of alpha-solanine to alpha-chaconine was 0.2 in Satu and 0.5-0.6 in Sini. In the second experiment, the total GA concentration +/- standard error was 75 +/- 4 to 96 +/- 11 mg kg(-1) fresh weight, and the ratio of alpha-solanine to alpha-chaconine was 0.3-0.4 in Satu. A high sodium selenate supplementation (0.9 mg of Se kg(-1) quartz sand) slightly decreased the GA content in Satu, but this decrease was not statistically significant. Furthermore, at this addition level the Se concentration increased to a very high level of 20 microg g(-1) dry weight, which cannot be recommended for human consumption. In both experiments, the Se concentration in tubers increased with increasing sodium selenate application levels. Our results show that acceptable application levels of selenate did not have an effect on the GA concentration in immature potato tubers.