A strain of Penicillium nigricans, which produces both the antifungal antibiotic griseofulvin and tremorgenic penitrem mycotoxins concurrently in static liquid culture, also elaborated both metabolites in submerged culture when stimulated by calcium chloride to sporulate. Maximum yield of penitrems (60 mg l-1) occurred within 5 d in a 60 l stirred fermenter, thus constituting the first significant process for penitrem production in submerged culture.