Since its founding in 1937, the National Cancer Institute (NCI) has supported a substantial program of information dissemination. Two peer-reviewed journals, begun in 1940 and 1959, are supplemented by a congressionally mandated International Cancer Research Data Bank (ICRDB), established in 1972. The NCI has made available online databases of published cancer literature and cancer research in progress for the past decade, using the National Library of Medicine (NLM) MEDLARS system. Recently, a clinical-practice-oriented cancer-information system called Physician Data Query (PDQ) has been developed for access at the NLM, as well as through commercial database vendors. The impact of the NCI information programs is currently under prospective evaluation.