Numerical abundance and composition of microzooplankton in the upper 200 m were studied from the central and eastern Arabian Sea during three seasons. Protozoans, comprising of ciliates (loricates and aloricates), flagellates and sarcodines were dominant, ranging from 55% to 91%. Among metazoans, nauplii and copepodite stages were common. Microzooplankton abundance was generally higher in the upper 100 m water column during all the three seasons. The column values were from 69,000 m sup(-2) to 188,000 m sup(-2) (inter-monsoon), 7350 m sup(-2) to 56,350 m sup(-2) (winter monsoon) and 10,800 m sup(-2) to 139,150 m sup(-2) (summer monsoon). Seasonal averages were 700 l sup(-1) , 130 l sup(-1) and 310 l sup(-1) respectively. A maximum of 5000 l sup(-1) was observed during summer at 5 m at a coastal station. Microzooplankton carbon in three different seasons ranged from a minimum of 4 mu g Cl sup(-1) during summer monsoon to a maximum of 36 mu g Cl sup(-1) during inter-monsoon and was higher than that of mesozooplankton. Peaks in population observed during intermonsoon season, when phytoplankton productivity was low and relatively high bacterial abundance was observed, indicated a microbial loop.