Sovner et al (1985) proposed that the presence of Down's Syndrome (DS) precludes the possibility of concomitant mama, and this is not a new claim, since Earl (1961) had stated that neither cyclothymia nor manic-depressive psychosis occurred in the mentally retarded. While Sovner et al conceded that cases of mania in individuals with DS may simply have gone unrecognised or unpublished, they felt this to be unlikely. However, lest this suggestion enter the canon, we present a previously unreported case of a young adult with both DS and recurrent mania.