Hospital Inpatient Enquiry data were analysed to determine trends in hospital discharges for pelvic inflammatory disease in England from 1975 to 1985. Cases where the disease was thought to be related to another condition, e.g. appendicitis, were excluded from the analysis. Discharge rates for both acute and chronic disease increased over the review period and there was a 28% increase in the discharge rate for total disease. Women in their 20s were most likely to be involved and this group showed the greatest increase in the discharge rate, both for acute and chronic disease. In the 20-24-year age group the rate of discharge for acute disease rose by 50%, from 125.6/100,000 in 1975 to 189.0/100,000 in 1985. Patients with a diagnosis of chronic pelvic inflammatory disease tended to be older than those with acute disease. Women who were divorced were more at risk of both acute and chronic forms of the disease than single or married women. Increase in the use of surgery to confirm the diagnosis occurred only for those with chronic disease. About a quarter of patients with acute disease had the diagnosis confirmed surgically, and this proportion did not change in the period studied, although laparoscopy increased as laparotomy decreased.