Some strains of Aspergillus niger and Bacillus licheniformis, which produce citric acid and alpha-amylase, respectively, in submerged fermentation, did not produce these products when grown on wheat bran in a solid-state fermentation system. Cultures that produced high titres of alpha-amylase in submerged fermentation were poor producers in the solid-state fermentation system and vice versa. These discrepancies indicate the need for intensive screening to select potent cultures particularly suited to the system concerned since it is clear that the cultures which are good producers in submerged fermentation processes cannot be relied upon to perform well in solid-state fermentations.