Abstract Fumonisins were produced by strains of Fusarium moniliforme and F. proliferatum on a medium consisting of 500 g yellow corn kernels and 500 mL distilled water added to a 30.5 × 61 cm autoclavable polyethylene bag. The corn was inoculated by drawing a suspension from a lyophilized culture into a sterile 5 mL syringe fitted with a 19 gauge needle and injecting 1 mL through the side of each polyethylene culture bag. Bags of inoculated com were incubated in the dark at 20° to 22°C for 4 weeks. Seven to 8 days after inoculation, holes were punched near the tops of the bags to promote aeration. After a 4 week incubation, cultures were soaked in chloroform–acetone (50 + 50, v/v) in 4 L flasks overnight to kill fungus and to remove water. Next, the culture media was filtered through 2 mm nylon mesh screens and air dried from 24 to 48 h. Fumonisin concentrations were determined by liquid chromatography/o-phthalaldialdehyde fluorescence. Confirmation was by gas chromatography/mass spectrometry. We observed that the 3 most important factors in the production of fumonisins in bulk corn cultures were temperature control, moisture, and aeration. Extraction by acetonitrile–water (50 + 50, v/v) for 30 min produced the highest yields of fumonisins. Measurable concentrations were reduced by as much as 50% when culture material was heated at 50°C overnight. Fusarium moniliforme strains consistently produced fumonisin B1 as the major component, but some strains of F. proliferatum produced fumonisin B2 and/or fumonisin B3 at higher concentrations than fumonisin B1. Results were calculated on the basis of dried culture material.