The bark of Cassipourea guianensis Aubl. (Rhitophoraceae) from South America yielded a bis-1,2-dithiolanyl pyrrolidine; its structure was identified as l-methyl-2,5-bis(4-hydroxy-1,2-dithiolan-3-yl)pyrrolidine, or gerrardine (1) an alkaloid that has been previously isolated from Cassipourea gerrardii (1). This known alkaloid was thus isolated for the first time from this plant species, and pmr and cmr data of the compound are shown for the first time in this paper. Antimicrobial testing indicated some effects (MIC, 50 pg/ml) against Candida albicans TA., and a weak activity (MIC, 100 pg/ml) against three others (Escherichia coli NIHJ JC-2, E. coli 0- 11 1, and Klebsiella pneumoniae DT) .