Although Yersinia enterocolitica has been isolated in a few cases in some tropical countries, it is more prevalent in cold European countries. Recently, several reports have incriminated pig and pork as the chief reservoirs of Y. enterocolitica. To determine the presence of this organism in Dacca, we attempted to isolate it from 212 stool samples from patients with a clinical picture resembling yersiniosis, 113 other stool samples from patients with diarrhoea, 30 appendices from appendectomized patients and 190 stool samples from animals with diarrhoea. No Y. enterocolitica was detected. This may be due to Dacca's warm climate: the 18-year average temperature for January (coldest month) is 18.5 degrees C. The effect of environmental temperature on Y. enterocolitica needs further investigation. An alternative explanation may be the prohibition on eating pork and the virtual absence of pig rearing in Bangladesh, a Muslim country. In fact, to date only one case of yersiniosis has been reported from a Muslim country (Iran).