The total glycoalkaloid (TGA) contents and individual glycoalkaloid compositions of foliage from 16 wild, tuber-bearing Solanum species of potential use in potato breeding were determined by using a combination of analytical procedures. A wide range of TGA contents was found (0.2-39.0 mg/g dry weight). Most of the species had higher TGA levels than Solanum tuberosum, cv. Katahdin (2.6 mg/g dry weight). Great diversity in individual glycoalkaloid composition was found among the species. Most species contained only a-solanine and a-chaconine, but glycoalkaloids not usually associated with commercial cultivars were found in several species. Glycoalkaloids (probably solamargine and solasonine) not previously found in any tuber-bearing Solanum species were found in Solanum berthaultii (PI 265858). This report also provides glycoalkaloid data on several previously unanalyzed species. The data emphasize the need for careful evaluation of glycoalkaloids as a potato quality factor in breeding programs which exploit wild Solanum species.