The pectinases produced byPenicillium frequentans were subjected to pectin- or sodium polypectate-PAGE. The fungus secreted one endo- and one exo-polygalacturonase during the first 10 h of incubation, either in media supplemented with pectin or in the absence of carbohydrate source. After 17 h of cultivation, another two exo-and three endo-polygalacturonases were detected in cultures supplemented with pectin. The results indicate that two constitutive polygalacturonases are secreted initially, followed by the synthesis of other inducible pectinases, in a sequential production of the pectinolytic complex. Monogalacturonic acid and sodium polypectate were better inducers for exo- than for endo-polygalacturonases, indicating that these enzymes are independently controlled.