Samples of various tissues and organs from healthy, sick and dead harbour seals (Phoca vitulina) from the North German Waddensea collected during the years 1974-1976 were analysed for copper, zinc, total mercury, cadmium, lead, and organochlorine pesticide residues (PCB, DDT, Lindane and Dieldrin). The investigations were carried out in order to increase our knowledge about the actual degree of heavy metal and organochlorine pesticide accumulation in these animals. The study was also directed towards a comparison of healthy and sick young seals and those found dead for a possible relation between the condition and concentration of pollutants in the organs. There was great variation within all series of compounds investigated, but in general the analytical data obtained indicated that high amounts of heavy metals and organochlorine pesticides can be present even in young seals. An age-specific increase in the mercury and cadmium content in liver samples could be demonstrated. The results are compared with data published by British and Dutch authors for other North Sea regions, and with a few exceptions, no significant differences can be established: cadmium (kidney) and DDT (blubber) contents in areas off the British coast are usually higher than corresponding values for seals from the German coast. There was no clear evidence that the concentrations of any of the compounds investigated had negative effects on the health of the seals. However, possible combined effects cannot be excluded.