Homicide rates for infants dropped suddenly between 1967 and 1969. The abrupt nature of this decline suggested the change was artifactual. Investigation suggests that two classification revisions instituted at this time were causes of this decline: changes in related codes set forth in the Eighth Revision of the International Classification of Diseases, Adapted, and revision of the standard certificate of death in 1968. Infant homicides may have been disproportionately underrecorded after 1968. (Am J Public Health 1983; 73:195-197.)