The sample included 135 children at high risk for drug abuse because their fathers had lifetime substance abuse disorders and 208 children at low average risk who were recruited at the Center for Education and Drug Abuse Research in Pittsburgh. Language ability was measured using WISC-III verbal IQ subtests and the Test of Language Competence. The performance of high-risk subjects was significantly poorer than the performance of low- average-risk subjects on several measures of language ability. The magnitude of effect increased between the two testings, indicating that high-risk subjects became more impaired over time. Findings also suggested that poor language mediation, as one facet of executive cognitive functioning, was a component of the liability for substance abuse. 26 references, 2 tables, and 1 figure