Tuber glycoalkaloids {TGA) in seven New Zealand potato culti vars were assessed before and after a period of exposure to light. Differences between cultivars were marked, TG.A. concentration ranging from 2.5 to 47.5 mg/100 g fresh weight, Ranking of cultivars was similar before and after exposure. Immature tubers had a higher initial TGA content than mature tubers and accumulated more TGA over the period of exposure. In 'Ham Hardy' tubers, TGA increased most rapidly during the first 20 days. TGA from potato tuber extracts contained three components, one of which was identified as solanine.