Comparative study of the breeding activity of Sphaeroma terebrans in the three major brackishwater lakes of Kerala viz., Vembanad, Ashtamudi and Veli Lakes and S. annandalei in the Ashtamudi Lake, in relation to the environmental factors in these lakes, showed that both the species are continuous breeders. Lower temperature tended to increase the breeding activity of S. terebrans whereas in S. annandalei higher temperature favoured the breeding activity. Higher levels of oxygen appeared to enhance the breeding activity of S. terebrans. Significant, multiple correlation was seen between the nutrients and breeding activity of both the species.