Technical Abstract: Fumonisins pose a tortuous problem for risk assessment. Unlike most mycotoxins, fumonisins of the B series (FB) are water soluble and unlike many other carcinogens are not metabolized nor react directly with DNA. Their toxicity is species-, sex-, and strain-dependent. FB1 was the first naturally occurring compound shown to inhibit ceramide biosynthesis. Ceramide is an intermediate in, what was in 1990, an obscure lipid pathway. One of the first effects of FB1 is increased apoptosis; a process normally considered to reduce cancer risk. FB is rapidly excreted and poorly absorbed; yet evidence of exposure can persist after FB is removed from the diet. <i>Fusarium verticillioides<i> was once described as a 'Mycotoxicological Miasma'. It should have been no surprise that structurally FBs are sphingolipid-like and sphingolipids are the 'Sphinx' of lipids. This presentation will include an historical account of the FB risk analysis from the recognition that moldy maize caused farm animal diseases until the first cancer evaluation of FB1 was completed in 2002. Nonetheless, although the USFDA has issued official guidance to industry, the fumonisin risk assessment is far from complete. For example, some studies suggest that FBs are not teratogenic and that fetal toxicity, when present is secondary to maternal toxicity. More recent data suggests, however, that neural tube defects can be induced in one mouse strain and the incidence is closely linked to altered folate receptor function. Thus, future issues could surface and they must be resolved if science-based risk assessment is to be the basis for future re-evaluation of regulatory guidelines or tolerances.