Conidiophore formation and sporulation can be induced inPenicillium sp. strain P 17 by an environmental factor—carbohydrate (carbon) starvation. Both surface and submerged mycelium, when transferred from synthetic medium to glucose-free salt solution, form conidiophores and sporulate, while in the control cultures on complete medium, vegetative growth continues. The time required for the formation of conidiophores, i.e. the induction interval, is 7–14 h and its length increases with the age of both surface and submerged mycelia. During the induction phase the mycelium undergoes autolysis, associated with degradation of energy motabolism involving the comsumption of reserve substances, a rapid drop in endogenous respiration and the endogenous reducing activity of the mycelium, a decrease in the labile phosphate concentration, proteolysis, an increase in the ammonia and orthopsphate concentration and exhaustion of readily oxidized amino acids from the pool. A transient increase in respiration occurs before differentiation of the conidiophores starts. During the second half of the induction phase, polyphenol substances and polyphenol oxidase appear in the mycelium.The enzyme is not induced by exogenous phenols. Its possible role in the sporulation of fungi is considered.