Malignant neoplasm has become the leading cause of death in Taiwan since 1982. There has been a decreasing trend for cancers of the stomach and cervix uteri, while an increasing trend has been observed for cancers of the lung, liver, oral cavity, colon and rectum, breast and prostate. International comparison and migrant studies have shown an elevated risk of hepatocellular carcinoma, nasopharyngeal carcinoma and cervical neoplasia in Taiwan. The national hepatitis B vaccination program, started in July 1984, has resulted in a significant decrease in childhood hepatocellular carcinoma in Taiwan. A decrease in prevalence of cigarette smoking has been observed among middle-aged men since the control of tobacco hazards was enacted in 1997. Free mass screening of cervical neoplasia and colorectal cancer has been implemented in the national health insurance program since 1995. Project-based screening for hepatocellular carcinoma, nasopharyngeal carcinoma and breast cancer among high-risk groups was started in 1994. Most cancer patients are diagnosed by pathological examinations and treated by surgical operation, chemotherapy and radiotherapy in major teaching hospitals in Taiwan. The Taiwan Collaborative Oncology Group has been organized to assess the efficacy of various treatment modalities through multicentric clinical trials. There has been a striking increase in expenditure for medical care of cancer patients. Cancer researchers mainly sponsored by the National Science Council and Department of Health are engaged in basic, epidemiological and clinical studies on major cancers in Taiwan. Major fields of the research include cancer genomics, gene therapy, molecular epidemiology and DNA vaccine.