Concentrations of total mercury and total cadmium in P. alba were determined by atomic absorption spectroscopy. The results were greatly affected by the type of tissue analysed, the locality where the scallops were collected and, to a lesser extent, by the length of the scallops. Mean concentration of mercury was 0.02 µg g^-1 wet weight (range 0.01-0.04 µg g^-1 wet weight) in adductor muscle, 0.02 µg g^-1 (0.01-0.03 µg g^-1) in gonads, and 0.04 µg g^-1 (0.01-0.11 µg g^-1) in viscera. Mean concentration of cadium was 1.0 µg g^-1 (0.3-1.9 µg g^-1) in adductor muscle, 0.9 µg g^-1 (0.5-1.4 µg g^-1) in gonads, and 7.7 µg g^-1 (3.7-1 5.1 µg g^-1) in viscera. The concentrations of mercury tended to decrease in samples from north to south and from east to west, and concentrations in the most western region of Port Phillip Bay were intermediate in value. Although the trends for cadmium were not so well defined, concentrations in the northern region were generally higher than those in the southern region.