Glycoalkaloids extracted from Solanum sodomaeum L. show antineoplastic activity against Sarcoma 180 in mice. Approximately 33% of the total glycoalkaloid content consisted of the triglycoside solasonine and 33% of the triglycoside solamargine. The remainder was a mixture of mono- and diglycosides in which the aglycone was solasodine. Single dose studies of these glycoalkaloids with mice containing Sarcoma 180 indicated that the ED50 was 9 mg/kg, whereas the LD50 was 30 mg/kg resulting in a therapeutic index of 3.3. Single dosages of 8 mg/kg given on two consecutive days resulted in inhibition of tumour progression with greater than 40% survival. In contrast, the use of the same dosages given on three or four consecutive days resulted in greater than 90% survival.