Cispentacin (( - )-(li?,2^)-2-aminocyclopentane- l -carboxylic acid) is a new antifungal antibiotic possessing potent anii-Candida activity. The 50% inhibitory concentration (IC50) and IC100 values of cispentacin against clinical isolates of Candida albicans were in the ranges 6.3~12.5 and 6.3 ~ 50/jg/ml, respectively, by turbidimetric measurement in yeast nitrogen base glucose medium. No significant activity wasseen against any yeasts and molds whentested by the agar dilution method using three different agar media; Knopp's agar, yeast extract - glucose -peptone agar and Sabouraud dextrose agar. This antibiotic demonstrated good therapeutic efficacy against a systemic Candida infection in mice by both parenteral and po administrations. The 50%protection dose (PD50) values after single iv and po administrations were 10 and 30 mg/kg, respectively. It was also effective in a systemic infection with Cryptococcus neoformans and in both lung and vaginal infections with C. albicans in mice. Cispentacin did not induce acute lethal toxicity at 1,000mg/kg by iv injection and 1,500mg/kg by ip and po administrations in mice.