The percentage data of 47 radiolarian coarser taxonomic groups in the surface sediments from the central Indian Basin was subjected to cluster and factor analyses. The R-mode cluster analysis resulted in 3 dominant clusters which represent surface, subsurface and deep water dwelling radiolarian groups. The Q-mode factor analysis resulted into three dominant factors. The factor-1 is characterized by Pyloniids group dominating the southwestern part with higher salinity (greater than 34.5/ppt), low sea surface temperature (less than 27 degrees C) and high potential primary productivity (greater than 0.2 mgC/m sup(3) /h) during the southwest monsoon. The factor-2 is characterized by Spongodiscids group dominating the northeastern part with lower salinity (less than 34.5/ppt), warmer SST (greater than 28 degrees C), and poor potential primary productivity (less than 0.2 mgC/m sup(3/h) during the southwest monsoon. The factor-3 is characterized by Euchitoniids dominating a transitional area between the two factors