The toxinogenesis of 10 strains of Penicillium granulatum, 5 of P. expansum, 4 of Aspergillus terreus, 2 of A. clavatus, P. thomii, P. urticae, P. italicum and 1 of P. claviforme was tested at 26 degrees C in Czapek's enriched liquid medium (8 p. 1000 glucose + 2 p. 1000 yeast extract). 6 strains of P. granulatum, 5 of P. expansum, 1 of P claviforme and P. thomii produced patulin after 9 days of culture. Mycotoxin concentrations recovered was between 0.2 ppm and 3127 ppm. Highly toxinogenic strains are Penicillium granulatum; but patulin in silages was not associated with P. granulatum.