A survey has been carried out to determine the levels of fumonisins in a variety of maize-based foods and cereals available in the UK. The fate of fumonisins during commercial processing of maize was also assessed at each stage of the process. Fumonisins were not detected in samples of barley, wheat, soya, oats, rice, corn syrup or oil, corn-on-the-cob, corn-fed chicken or wheat flour tortilla. Despite detectable fumonisin contamination in samples of the original maize, fumonisins were not detected in samples of the food products obtained from commercial maize processing. Low levels were detected in samples of tacos and in some foods containing corn-based thickeners, such as instant semolina pudding and instant custard powder. Approximately 78% of corn snack samples contained fumonisins (11-220 micrograms/kg), while 24% of breakfast cereals contained total fumonisins at between 11 and 194 micrograms/kg. Although none of the ready-made popcorn samples contained detectable levels of fumonisins, 46% of popping corn samples and microwaveable popcorn contained fumonisins at 14-784 micrograms/kg. The highest levels of fumonisins were detected in samples of polenta with concentrations ranging from 16 to 2124 micrograms/kg. Overall, fumonisins were detected in 26% (76) of the 291 retail samples analysed.