Fifty-eight individuals with Hailey-Hailey disease were studied to delineate the clinical features, response to treatment and prognosis. The disease generally presented between the second and fourth decades, but the morphology of lesions was varied and a delay in diagnosis was common. Nail changes have not been documented in previous studies of Hailey-Hailey disease, but asymptomatic longitudinal white bands were present in the fingernails in 71% of 38 patients examined and are a helpful physical sign. The disease is predominantly flexural. Friction and heat or sweating exacerbate the lesions and pain may limit physical activities. The prognosis was assessed in 27 patients with longstanding disease and the long-term outlook is generally good. Seventeen patients had improved and the disease was static in seven patients. Three patients deteriorated with age. Topical corticosteroids with or without added antibiotics were an effective treatment.