Foliar leptine levels in 60 Solanum chacoense accessions were determined in a search for high-leptine plants that might be useful in breeding for resistance to the Colorado potato beetle, Leptinotarsa decemlineata Say. New methods were developed for detecting and quantifying leptine glycoalkaloids. A wide range of levels (<2-98 mg % fresh weight) was found among the accessions; most (42 of 60) apparently did not synthesize even traces of leptines. Among six sibs individually sampled from one accession, levels ranged from <2 to 306 mg % in replicated analyses. The results indicate that leptine glycoalkaloids are segregating widely among and within S. chacoense accessions. Tubers from high-leptine clones did not synthesize leptines even when greened or wound healed.