Since then, hundreds of studies have been done of the intelligence quotient (IQ) of delinquents. As IQ tests improved and the problem was approached with greater methodological sophistication, differences between the IQ's of delinquent and nondelinquent populations grew smaller. However, systematic review indicates that delinquents generally have mean IQ's of about 92, 8 points lower than the general population. Performance deficits in problem children and delinquents have been found to be largely in verbal abilities. It is suggested that lower IQ may be one of many factors placing children at risk for poorer parenting, lowered academic performance, and deficient social skills and interactions -- factors that also may be associated with greater risk of subsequent juvenile delinquency. 51 references.