Cultures of molds from the genera Penicillium (25 isolates) and Aspergillus (18 isolates) were inoculated onto YM agar fortified with different concentrations of potassium sorbate to determine their abilities to grow in the presence of this compound. Molds were incubated for up to 30 d at 25 or 4°C. Nine of the penicillia grew in the presence of 3000 ppm or more of sorbate at both temperatures. All of these molds were isolated from sorbate-treated cheeses. None of the aspergilli grew in the presence of 2000 ppm or more of sorbate and only three strains grew in the presence of 1000 ppm of sorbate at 25°C. None of the aspergilli grew in the presence of 500 ppm of sorbate at 4°C.