Forty-two analogues and reaction products derived from T-2 toxin or neosolaniol were assayed for their cytotoxicity to cultured mouse lymphoma cells. Structure-activity relationships confirmed the stereospecific nature of the cytotoxic action of T-2. Cytotoxicity was particularly susceptible to changes at C3, C4, C9, and C10 but was relatively unaffected by changes at C8, which appears to represent a region of steric tolerance in the interaction of T-2 with a cellular constituent. The most potent compounds were T-2, diacetoxyscirpenol, and a series of C8 ester analogues 11 and 31-35.