The therapeutic efficacy of Bioflorin (Streptococcus faecium SF68; Gipharmex, Milan, Italy) in acute watery diarrhea was evaluated in 183 Bangladeshi adults. Vibrio cholerae organisms were isolated from stool cultures in 114 patients, and enterotoxigenic Escherichia coli organisms were isolated in 41. In addition to IV rehydration, patients were randomly assigned to receive either capsules of Bioflorin containing 1 X 10(9) of live SF68 or capsules of placebo containing killed SF68 once every 8 hours for 3 days. No other drugs were allowed during this period. Bioflorin was well tolerated. It is concluded that Bioflorin has no demonstrable antidiarrheal property in adults with acute diarrhea due to V. cholerae or enterotoxigenic E. coli infection.