Occurrence, abundance and seasonal fluctuations of Culicoides peliliouensis in the mud and sand flats of Hooghly estuary were studied in relation to some important environmental parameters (air temperature, soil temperature, soil moisture, rainfall, salinity, dissolved oxygen and pH of interstitial water, organic carbon, available phosphorus, percentage of sand, silt and clay of soil) at three stations in and around Sagar Island during July 1982 to June 1984. They were more or less found throughout the year, withmaximum abundance during postmonsoon and minimum during premonsoon. Several statistical analyses have been computed to study the relation between population of C. peliliouensis and all ecological parameters. Results of ANOVA indicate that almost all ecological parameters varied significantly over months, stations and years, whereas the population of C. peliliouensis varied significantly only over months and stations. Soil temperature, rainfall, organic carbon and available phosphorus appear to be the major factors controlling their distribution in the intertidal habitat as evident from correlation coefficient analysis. Multiple regression analysis shows that the combined effect of all parameters is positively significant at all the stations.