Aureobasidium pullulans CBS 591.75 produced poly(malic acid) (PMA) from glucose, sucrose and succinate. A suitable glucose concentration for PMA production was about 50 g/L. Trifluoroacetic acid inhibited while malonate, maleate, succinate and malate increased the production of PMA; for example supplementation of succinate up to 6.5 g/L to the medium for example increased PMA production by 44%. Go-feeding of trifluoroacetic acid plus succinate or malate relieved the inhibition by trifluoroacetic acid. These results showed that PMA synthesis is probably related to the citric acid cycle and also indicated that isocitrate lyase and malate synthase participate in PMA biosynthesis.