Numerous studies have addressed the regulation of fungal ODC in response to exogenously added polyamines. In the cases examined, Physarum polycephalum (Mitchell and Wilson, 1983) , Saccharomyces cerevisiae (Fonzi, 1989; Toth and Cof®no, 1999) and Neurospora crassa (Barnett et al., 1988; Williams et al., 1992) , added polyamines, especially spermidine, result in signi®cant repression of ODC activity. The mechanisms of repression seem to vary from fungus to fungus and are apparently different from the mechanism of polyamine-dependent regulation of ODC in higher eukaryotes. In some cases, the existence of an antizyme-like protein has been suggested but has either been disproved, as in the case of N.crassa (Barnett et al., 1988) , or has never been substantiated, as is the case with S.cerevisiae.