Past and present Canadian experiences with biological testa for controlling the quality of wastewaters are discussed. Test use has evolved from data acquisition on acute toxicities, to physicochemical and biological parameters being regulated and monitored by industrial sector in the 197013, and hazard assessments conducted by the 1980s. At a time when Environment Canada is reviewing its ecotoxicological procedures, new opportunities for waste assessment with "second generation" biotests are emerging. Recent experiences suggest that small-scale, sensitive, biological testa can be employed for environmentally and economically effective control of effluents entering aquatic environments.It is also expected that biotesting activities will increase because of new environmental strategies and regulations. These will stimulate biological research and development, and promote a partnership between ecotoxicology, environmental chemistry, and biotechnology.