Fifty patients with bullous pemphigoid were investigated over periods of up to 7 years. Sequential studies of circulating basement membrane zone (BMZ) antibody titres revealed two groups of patients: 44% had a high initial titre (> 1:160) and 56% had a low initial titre (< 1:160). Subjects with titres > 1:160 continued to have high titres, whereas in those with lower titres the BMZ antibodies usually became undetectable after 4 months. The BMZ antibody titres were of no prognostic value. High titres remained high even in patients who were in remission and off treatment, and in these subjects, there was no evidence of a change in the IgG subclass. The initial BMZ IgG antibody titres showed a highly significant correlation with total serum IgE concentrations. A significant correlation also existed between total serum IgE and IgG4 concentrations, although not between the serum IgE and the peripheral blood eosinophil count. No anti-BMZ antibody of IgE class was found, nor specific IgE against inhalants and foods identified, and the significance of the high total serum IgE remains unexplained. The majority of those followed for more than 2 years were able to stop their steroid therapy without further blistering: this confirms that pemphigoid tends to be a self-limiting disease. Nine patients had a recent history of malignant disease, and this is no more than would be expected for this age group of patients: however, 3 patients presented with pemphigoid and figurate erythema and all died of neoplastic disease, suggesting that such patients should be investigated thoroughly for neoplasia.