A total of 110 clinical isolates of Vibrio cholerae O1 biotype El Tor serotype Ogawa isolated in a recent outbreak from different districts of Teheran, Iran, was subjected to 99 carbon source utilisation tests, ribotyping and toxinogenotyping. PCR showed that the genes encoding cholera toxin (ctxA), toxin co-regulated pilus (tcp), accessory cholera enterotoxin (ace) and zonula occludens toxin (zot) were present in 100%, 100%, 97.3% and 99.1% of the isolates, respectively. Restriction fragment length polymorphism (RFLP) study of the BglI-digested DNA probed with five oligonucleotides targeting the conserved regions of 16S and 23S rRNA genes revealed a similar ribotype pattern for 109 isolates. All but one isolate showed ribotype pattern B21a, containing seven bands with molecular sizes ranging from 11 to 3.9 kb. The toxin gene restriction pattern (toxinogenotype) showed that the isolates carried either three or two copies of the toxin genes (ace, zot, ctx) which were recognised as TB41a and TB69 patterns, respectively. Overall, the ribotyping data showed that, despite biochemical differences in 12 of the 99 carbon sources, most of the isolates studied belonged to a single clone.