Production of phytochelatins (PCs) in response to cadmium uptake in the benthic macroalgae Vaucheria compacta and V. debaryana (Xanthophyceae) was investigated. The algae synthesized thiol-containing peptides, identified by means of high-performance liquid chromatography as PC2, PC4 and PC4. In both algal species the level of PCs increased with time of cadmium exposure and was dependent on external cadmium concentration. V. compacta synthesized significantly more PCs than V. debaryana. Exposure of the algae to cadmium at low temperature and in darkness resulted in a significant decrease in PC content over the time interval tested (3 days).