Both the true incidence of meningococcal disease and the proportion of cases of meningococcal meningitis notified in England and Wales are not known. A comprehensive search for cases of meningococcal disease within a defined boundary, that of Greater Manchester, was made using various sources of information, for 1985. Sixty-seven per cent of cases of meningococcal meningitis and 63 per cent of meningococcal disease were notified. Fifty-seven percent of cases were referred for further tests to the United Kingdom meningococcal reference laboratory. Only 79 per cent of cases were identifiable on Hospital Activity Analysis (HAA) data. Information was also sought on sources of notification, notification delay, delay in laboratory diagnosis and length of stay. There is considerable potential in reducing notification delay, after comparing dates of laboratory diagnosis and notification. Notification should be more complete. In the absence of this ideal, surveillance of meningococcal disease needs to rely on various sources of information to gain a complete picture of the disease. Management of contacts of cases and of outbreaks is impossible without prompt and complete notification.