Records of approximately 310,000 patients admitted to the 10 hospitals in Botswana between 1960 and 1972 have been studied and details of 1445 patients with malignant tumours abstracted. For the 894 tumours for which there was some supporting evidence--at best histological proof and minimally a clinical description of symptoms--proportional frequencies have been calculated for all sites and comparison made with the findings of other surveys. Cancer of the cervix uteri is overwhelmingly the most commonly occurring malignant tumour and the proportional frequency is among the highest observed in Africa south of the Sahara. Skin tumours are unusually common for Southern Africa in both sexes. In males, penile and prostatic tumours have a relatively high frequency whilst the frequencies for liver and lung are lower than in other parts of Southern Africa. Oesophageal cancer in males has a moderate frequency. Other tumours which show a marked variation of frequency within Africa--Kaposi's sarcoma and cancers of the stomach and bladder--are all low in frequency in Botswana. Tumours which are rare throughout Africa but common in Western Europe and North America--cancers of the colon, rectum and corpus uteri--are also rare in Botswana.