The role of enterotoxigenic Escherichia coli (ETEC) as etiologic agents of diarrhoea in infants aged less than six months was assessed in a hospital based study in Calcutta, India. Of the 218 cases examined, ETEC strains were isolated from 26 (11.9%) cases. Among these, in 17 cases ETEC was the sole infecting pathogen (p = 0.0085). Of the 26 isolates (each isolate representing a case), 24 were distributed among seven different O:K:H serotypes and two different colonization factor antigens (CFAs) I and II. Two of the remaining isolation were untypable, non-haemagglutinating, and were non-hydrophobic as measured by the salt aggregation test (SAT). Of the 26 ETEC strains detected, 15 (57.7%) produced heat-labile toxin (LT) only, 8 (30.8%) liberated heat-stable toxin (ST) only, and the remaining 3 (11.5%) produced both LT and ST. No ETEC strain was isolated from the 102 age-matched controls included in this study. All the ETEC isolates were multiple drug resistant. The study showed that the diarrhoea due to ETEC was of brief duration, mostly within the range of 3 to 7 days.