A total of 610 samples of marine sewage discharges, polluted seawater and shellfish have been analysed for human enteric viruses and indicators of faecal/sewage pollution. Viruses were recovered by ultrafiltration from water samples of up to 10 litres, and by extraction from 50 g samples of shellfish meat. Detection of viruses was by cytopathogenic effect in primary vervet kidney cells. Some samples were tested for rota- and hepatitis A virus antigens using immunosorbent assays. Of the 202 samples from which viruses were cultured, 45% yielded enteroviruses and 87% reoviruses. The ratio of counts of viruses and indicators varied extensively in samples of both seawater and shellfish. Viruses or their antigens were detected in a number of samples which yielded negative results in conventional tests for at least one indicator. The results show that currently used quality criteria based on coliform indicators have shortcomings with regard to viruses. These findings, as well as experience and policies in other parts of the world, were applied in formulating revised quality criteria for seawater used for recreational purposes, and shellfish meat intended for human comsumption. The recommended criteria include limits for human viruses, faecal coliform bacteria, faecal streptococci and coliphages. The test methods used in conjunction with these criteria are considered important, and methods for viruses should be able to detect reoviruses.