Malignant neoplasms are responsible for more than half a million deaths annually and 22.5% of all deaths in the United States. Cancer is the second leading cause of death overall and the leading cause of death among Americans aged 35-64. Within the next decade it may become the leading cause of death. Cancers of digestive and respiratory organs are responsible for 53% of all cancer deaths. Certain subgroups are at elevated risk for various cancers. For example, sun-sensitive or excessively sun-exposed young white adults, young black women, and elderly patients are at increased risk for cutaneous melanoma, breast cancer, and colon cancer, respectively. Black men have the greatest risk for both lung cancer and cancer of the prostate. Acute lymphoblastic leukemia and solid tumors of the brain and nervous system are the most frequent forms of malignancy occurring among children less than or equal to 14 years. Office screening is the traditional method for identifying cancer victims as early as possible. A suitable screening test should be rapid, simple, inexpensive, and impose minimal discomfort. There must be a window of opportunity available to identify the cancer during a detectable preclinical phase, and therapeutic modalities must be available to alter progression. An office screening test for cancer may have any one of four outcomes, and three of them are bad. False negatives are the worst adverse outcome because cancer remains undetected despite screening. An epidemic of lung cancer, caused by cigarette smoking, is occurring in all race and sex groups. If Americans stopped smoking, 87% of lung cancer deaths could be prevented. Tobacco abuse also is a major risk factor for cancer of the esophagus, larynx, and oral cavity. Cigarette smoking is a contributing factor for cancer of the bladder, kidney, and pancreas, and it has been associated with both cervical cancer and cancer of the stomach. Smoking and smokeless tobacco cessation endorsements, messages, and programs must be part of routine disease prevention and health promotion activities in every primary care practice. More than 1 million Americans became new cancer victims last year, and more than 1 million additional cases will be detected this year. Because of the striking variability in state and regional patterns of various forms of cancer, geographic location of a practice may influence the frequency of cancers seen. Four sites (breast, prostate, lung, colon, and rectum) were responsible for 55% of cancer mortality and 56% of all new cases of cancer detected during 1991.(ABSTRACT TRUNCATED AT 400 WORDS)