SUMMARY.Two‐hundred isolates, comprising 87 species of Chlorophyta, were obtained from sites along the Rivers Hayle and Gannel. which drain the ancient mining region of Cornwall. All isolates were tested for sensitivity to copper, lead, zinc and cadmium. In general, isolates were resistant to the metals normally present in their habitats. However, the distribution of metal sensitivities of the algae from a given site was broad; the effect of metal pollution was to shift the median response of a population toward higher metal resistance. Resistant algae of two general classes were identified: some normally sensitive species were metal‐tolerant, presumably through genetic adaptation; other species were metal‐resistant even when isolated from a non‐polluted habitat. Many isolates of both types displayed multiple‐resistances or co‐tolerances. For example, copper tolerant isolates from high copper sites tended to be also lead resistant; however, algae from high lead sites were usually very copper sensitive. Zinc and cadmium resistances also were correlated among isolates from both zinc‐polluted and non‐polluted sites. General metal‐insensitivity seemed to be common, particularly among gelatinousChlamydomonasandGloeococcusspecies. Thus, several evolutionary strategies appear to coexist among algae from metal poll