The marine biodiversity of the south-east coast of India is rich and varied. This article deals with the availability of molluscs from the trash fish from the Cuddalore coast, Tamilnadu, south-east coast of India, viz., Mudasalodai (11°29′N 79°46′E) and Cuddalore (11°42′N 79°46′E) landing centres. A survey has been done to estimate the composition of molluscs from October 2007 to September 2008. About 250 trawlers from Cuddalore and 200 trawlers from Mudasalodai were engaged in fishing activity every day up to a depth of 30–80 m. A total of 59 species belonging to 35 genera from 25 families were recorded at Station 1 and 57 species belonging to 32 genera from 24 families were identified at Station 2. The most diverse families were Muricidae, Conidae, Arcidae and Veneridae at both stations. The Shannon diversity index of gastropods varied from 2.27 to 4.71 and bivalves varied from 1.82 to 2.52, the species richness of gastropods varied from 2.75 to 6.27 and bivalves varied from 1.42 to 1.75. The species evenness in the gastropods was between 0.58–0.90 and 0.57–0.74 in gastropods and bivalves respectively. Seasonal contribution of gastropods attained maximum in pre-monsoon and minimum during the summer at both stations. At Station 1 bivalves attained maximum in pre-monsoon and minimum was recorded during monsoon. Seasonal contribution of bivalves at Station 2 was high in post-monsoon and minimum in the summer.