Samples of the green mussel, Perna viridis, the brown mussel Perna perna and the parrot mussel were collected from Kadiyapattinam of Kanyakumari coast and their biochemical composition and the levels of heavy metal contamination were analyzed. The results of this study showed that the biochemical composition of the mussels did not very much. The specimens of all the three species of mussels were found to be good aquatic invertebrates for human consumption. P. viridis contained higher proportion of protein than Perna perna and the parrot mussel. Perna perna and the parrot mussel contained more lipid, ash, carbohydrate, and fibre; and their caloric values were also more than that of Perna viridis. Perna perna had the highest moisture content (78.21%) followed by the parrot
mussel (19.47%) and Perna viridis (20.30%). Concentrations of the heavy metals (Cd, Cu, Pb, Cr, As, Ni and Se) in the edible portions of the samples were within the values recommended by the WHO. Mercury was not detected and so these mussels are safe for the consumers. The order of concentrations of minerals found in the mussel samples was: K > Na > P > Ca > Mg > Fe > Zn > Mn. Potassium content was more than the other elements. It was evident from the study that in the soft tissue of all Perna species the concentration of essential minerals was higher than the nonessential metals. Kadiyapattinam mussels are a rich source not only of protein but also of all the other micro and macro minerals. The soft tissues of all the mussels had low levels of heavy metal concentration, and this indicates a comparatively lower heavy metal contamination of Kadiyapattinam coast. Mussels are also a rich source of nutritional components and could be used as human diet in place of other fish so as to reduce the pressure on sea foods.