Cancer incidence, mortality and survival statistics for the UK are routinely available; however, data on prevalence, which is generally regarded as an important measure for health planning and resource allocation, are relatively scarce. Eight cancer registries in the UK, covering more than half the population, provided data based on >1.5 million cases of cancer. Total prevalence was calculated using methods developed for the EUROPREVAL study, based on modelling incidence and survival trends. The prevalence of cancers of the stomach, colon, rectum, lung, breast (in females), cervix uteri, corpus uteri and prostate, melanoma of skin, Hodgkin's disease, leukaemia and all malignant neoplasms combined, was estimated for the UK for the end of 1992. Overall, approximately 1.5% of males and 2.5% of females in the UK population at the end of 1992 were living with a diagnosis of cancer. These proportions increased steeply with age, with approximately 7.5% (7.3% and 7.8%, in males and females, respectively) of people aged > or =65 years living with a diagnosis of cancer. Of the individual cancers, by far the highest prevalence (almost 1%) was seen for breast cancer in females; more than one in three of all living female cancer patients had been diagnosed with breast cancer. For males, around half of prevalent cases had been diagnosed >5 years previously and 30% >10 years previously; for females, these figures were both higher, at approximately 60% and 40%, respectively. The estimates of prevalence presented here comprise: recently diagnosed patients in need of treatment and monitoring; long-term survivors, some of whom will nevertheless eventually die from the cancer, while others may be cured of the disease; and patients in the terminal phase who are dying from the cancer. Further work should attempt to identify the proportions of patients in the different phases of care in order to optimise the use of prevalence estimates in health care planning.