We report an outbreak of a "rash" syndrome in patients attending methadone clinics in New South Wales. It presents with a pruritic, exanthematous or purpuric rash involving the trunk, limbs, palms and soles, which develops over a week and proceeds in most patients to desquamation (mainly of palms and soles) persisting for 3-4 weeks. Mucosae are not involved, and patients are generally systemically well. To date, the rash has affected 22% of 316 patients attending one methadone clinic in western Sydney, as well as patients in clinics elsewhere in Sydney and rural NSW. The aetiology is as yet unknown.