Eddies are ubiquitous in the ocean and are products of geophysical turbulence. They develop from the hydrodynamic instabilities and are known to alter the physical and biochemical properties of the ocean. In the north Indian Ocean, these changes in the hydrodynamical and biochemical properties are a response to the seasonal reversal of monsoon winds. Off the twin seas of the north Indian Ocean, the Arabian Sea (AS) responds to this seasonal reversal more directly, whereas its eastern counterpart the Bay of Bengal (BOB) deviates from the norm. Apart from the seasonal reversal of the monsoon winds, BOB is influenced by the remote forcing via Rossby waves and coastally trapped Kelvin waves. Though the presence of eddies were reported in the BOB as early as 1950’s, their genesis and evolution have not been subjected to intense scrutiny. Present study is an attempt in this direction and to decipher their role. The attempt in this thesis was to study the characteristics and role of eddies in the Bay of Bengal. A suite of data sets has been used to accomplish this objective. To this end the evolution and the generating mechanisms were studied first followed by their role in the hydrography, circulation and in the distribution of nutrients and chlorophyll. The study brings out the role eddy in mediating physical, chemical and biological changes.