The National Health Service Central Register (NHSCR) and direct follow-up were used to document ovarian and fallopian tube cancers in 22000 women from 1986 to 1993. Direct follow-up identified 47/49 cases (96%) and the NHSCR 38/49 (78%). NHSCR ascertainment was incomplete and direct follow-up provided additional information. These findings have implications for interpretation of national cancer statistics and for use of the NHSCR in research trials.