Lysozyme activity of two commercially important edible bivalves, namely Perna viridis (Linnaeus) and Meretrix casta (Chemnitz), was analyzed against Micrococcus luteus. The results of this study indicated that the extract, prepared by homogenizing the mantle fluid and meat, had more lysozyme activity as compared to the acetic acid extract. The extract of P. viridis showed a better activity than M. casta. Partial purification of lysozyme was carried out using gel filtration chromatography and initial ion (IE) exchange chromatography.