The occurrence of histologically diagnosed primary malignant tumors in Saudi and Yemeni patients in Gizan Province over the 11 years from 1982 to 1992 was analyzed. During the study period, 1398 malignancies of known primary site were seen in males and 972 in females. In common with other parts of Saudi Arabia, the overall incidence of malignant disease was low by Western standards with lymphoreticular malignancies relatively common and tumors of lung, bowel, breast and the female genital system relatively uncommon. Some malignancies are more common in Gizan Province as compared to elsewhere in Saudi Arabia. Oral cancer was the most common malignancy in females and the most common overall, probably due to widespread use of oral tobacco preparations. Liver cancer was the most common malignancy in males, reflecting the endemic nature of hepatitis B in the area. The incidence of bladder cancer, and particularly of squamous carcinoma of the bladder, was also more, probably due to the high incidence of schistosomiasis in the area. No significant trends in incidence of specific malignancies were noted over the 11-year study period, even though the period has been marked by dramatic and unprecedented changes in lifestyle and public health.