This report investigates the relationship between birth defects and reproductive outcomes versus paternal TCDD levels among children and conceptions of members of Operation Ranch Hand, the unit responsible for the aerial spraying of herbicides in Vietnam and a comparison group. At a baseline physical examination in 1982 and again in 1985 and 1987, participants were asked to report occurrences of birth defects, miscarriages, stillbirths, infant deaths and neonatal deaths of their children. The birth defect status and outcome of all conceptions (N = 10,843) fathered by participants were verified by medical record review. Of these, 8,099 resulted in live births and birth defect status verified for 8,090 (99.9%). During the same period, the Air Force collaborated with the Centers for Disease Control to assay blood of the 1987 physical examination participants for 2,3,7,8 TCDD. The final interpretation of these data is deferred, pending further analyses.