Abstract : 1. The total lipid contents of four bivalve molluscs (Crassostrea gigas, Mytilus edulis, Ruditapes philippinarum, Cerastoderma edule) were estimated by two methods, one colorimetric the other gravimetric. 2. No significant differences were evident between the two methods. 3. The energy value of the total lipids, estimated by microcalorimetry varied throughout the year (minimum 29.05, maximum 40.88 joules/mg), with an annual mean of 34.83 ± 2.29 joules/mg.