Abundance and seasonal fluctuations of two larvae of tabanid insects viz. Atylotus agrestis and Tabanus striatus in the mud and sandflats of Hooghly Estuary were studied in raltion to some important environmental parameters at three stations in and around Sagar Island during July 1982 to June 1984. A.agrestis was abundant throughout the year, maximum during postmonsoon and minimum during premonsoon, whereas T.striatus was almost absent during premonsoon and maximum recorded in monsoon. Results of ANOVA indicate that almost all ecological parameters were varied significantly over months, stations and years, but the populations of these two species varied significantly only over months. Soil Temperature, soil moisture, salinity, dissolved oxygen, pH, organic carbon and available phosphorus appear to be the major factors controlling their distribution in the intertidal habitat as evident from correlation coefficient analyses. Multiple regression analyses show that the combined effects of all parameters on both the species were positively significant at all the stations.