A defined solid medium has been used to examine the responses ofAureobasidium pullulans, Saccharomyces cerevisiaeandSporobolomyces roseusto cadmium, copper and zinc. Experiments where aliquot volumes of metal salt solutions were added to wells in the centre of agar plates revealed marked differences between these organisms. The yeast‐like fungusA. pullulanswas the least sensitive butS. cerevisiaewas more sensitive to cadmium than zinc: the reverse was true forS. roseus.Quantitative data, which complemented the qualitative results, were obtained by measurement of metal concentrations in the plate