One hundred and seventy-two cases of intracranial abscesses, obtained from Neurosurgical and Centralised Autopsy Records for Northern Ireland for the 30 years, 1947--1976, have been reviewed. The incidence of the disease has fallen from five to three per million of population per year over the past three decades. Intracranial abscesses were three times as common in males as in females. Twenty-nine per cent of the abscesses were in the temporal lobe, 25% frontal, 10% parietal, 6% cerebellar, 3% occipital, and 7% were either subdural or in deep sites such as the thalamus; the remainder (20%) were multiple. Multiple and occipital abscesses were all fatal, temporal and parietal abscesses were associated with a 65% mortality, and 45% of patients with frontal abscesses died. Chronic suppurative otitis media was the single largest cause, and it was the only aetiological factor to have shown a progressive decline over 30 years. For those seen and treated in the neurosurgical unit the mortality was 53%, but if those obtained from the necropsy records were included the overall mortality was 70%.