In the period 1985-1996 concentrations of mercury, cadmium, lead, copper, zinc and chromium in cut trough shell (Spisula subtruncata) sampled on 11 stations on the Belgian Continental Shelf were determined. On the whole, contents of trace metals showed a tendency to decrease. No significant differences in concentrations were found between the stations, except on one site for lead and chromium. Average concentrations (all stations) were (in mg/kg wet weight): 0.02 for mercury, 0.08 for cadmium, 0.38 for lead, 2.5 for copper, 12.7 for zinc and 0.47 for chromium. These values were well below legally authorized limits.