As awareness of the huge human and other costs of injury has grown, research has expanded. There has not been any standard set of terminology for use in this research. As a result, research and surveillance data are too often difficult to interpret and compare. To overcome this impediment to gains in needed knowledge about childhood injuries, a conference was held in 1989 by the National Institute of Child Health and Human Development to develop a set of standard definitions. The full conference report is available from the US Government Printing Office. This report presents excerpts, emphasizing those--core--variables likely to be of use to the largest number of investigators. The conference recommendations presented address cross-cutting factors (age, race/ethnicity, location, socioeconomic status, and biopsychosocial development), effect modifiers (exposure, medical risk factors, substance abuse, time, injury severity, and social risk factors), and specific injuries (motor vehicle injuries, central nervous system injuries, falls, fire/burns, drowning, and violence). It is expected that childhood injury investigators will strive to meet the recommendations of this conference and that use of these definitions will lead to improvements in research and, ultimately, to revision of the definitions.