Processing speed subtests are components of widely used intellectual assessment instruments. Many researchers interpret these measures as assessing a unitary construct, but there is a question concerning the constructs assessed by these measures and, ultimately, their interpretative utility. Coding and Symbol Search from the Wechsler Intelligence Scale for Children-Third Edition (Wechsler, 1991), Visual Matching and Cross Out from the Woodcock Johnson Tests of Cognitive Ability-Revised (Woodcock & Johnson, 1989), and Speed of Information Processing from the Differential Ability Scales (Elliott, 1990) were administered to 102 volunteer participants. Using regression analyses, performance on each of these tests was predicted by motor speed and/or number facility factors. Individual differences in motor speed were found to be related to each of the five processing speed measures, whereas number facility was related to three of the measures. (Contains 5 tables.)