A total of 514 samples of acute diarrhoeal stools received over a period of four months yielded 315 isolates morphologically and biochemically resembling V. cholerae. Out of 315 isolates, 223 (70.8%) were identified as V. cholerae 01, 20 (6.4%) as 0139 and 42 (13.3%) as 010. Thirty (9.5%) isolates did not agglutinate with any of the available antisera. All V. cholerae 010 isolates showed complete homogeneity in their biochemical and physiological properties. This strain appears to be closely related to El Tor biotype of V. cholerae 01, since it was positive for some of the tests used for identification of El Tor. The ability of strain 010 to grow in the presence of 6 per cent salt provides it the status of an important environmental pathogen. Acquisition of some virulence genes from El Tor vibrios by this strain 010 appears to be one of the mechanisms involved in the emergence of this serogroup.