Summary The confusing terminology in the literature reflects the diverse presentations and inter-relationship of the mucocutaneous syndromes (MCS). An historical review is presented in an attempt to clarify the terminology and relate it to the experience of these disorders in one infectious disease unit. Over a 31-year period (1948–1979), 78 patients with MCS were admitted to the Infectious Disease Unit (I.D.U.) of the City Hospital, Edinburgh. Of these 56 were fully documented and were broadly comparable with patients from other earlier series except that associated infections were diagnosed in a higher proportion of cases (46 per cent). Mycoplasma pneumoniae was the commonest single organism identified. Since associated infections are probably more common than was previously suspected, all patients with MCS should have a wide range of microbiological investigations carried out. This report also confirms the well-known association of MCS with medication and especially with antimicrobial agents, a factor which confuses both aetiology and pathogenesis. Clinical similarities between MCS and Kawasaki disease are noted and discussed. HLA typing of patients with MCS suggested an association with BW15, and since this antigen has also been implicated in Kawasaki disease common immunogenic mechanisms may be operating.