A population-based cancer registry, in operation in Shanghai since 1963, services an urban area which has a total population of about 5.7 million. This report provides a brief description of our method for collecting cancer cases and incidence data for 1973-77. During this period, annual average age-adjusted cancer incidence rates for all sites were 246.9 and 169.1 for males and females, respectively. Cancers of the stomach, lung, liver, esophagus, and colon/rectum were frequently seen in both sexes; in addition to those mentioned above, cancers of the cervix uteri and breast were common in females. A rapid increase in incidence rates of lung and liver cancers and a marked decrease in cancer of the uterus (mainly of the cervix) were observed. In comparison with cancer incidence rates in other countries, those for cancers of the stomach, liver, and esophagus in both sexes and the rate for lung cancer in females in the Shanghai urban area were extremely high; contrastingly, rates for cancers of the colon, rectum, corpus uteri, ovary, and prostate gland were extremely low.