This study investigated the Wechsler Performance IQ (PIQ) or Perceptual Reasoning Index (PRI)/ Perceptual Organization Index (POI) change over time and its relation to ability levels. PIQ or PRI/ POI was analyzed because of the known sensitivity of nonverbal scales to the Flynn effect. Scores were analyzed using two methods. First, analysis of covariance was applied to the combination of four representative samples of individuals who were administered the following pairs of Wechsler batteries in counterbalanced order: "Wechsler Preschool and Primary Scale of Intelligence-Revised" (WPPSI-R) and WPPSI-III (N = 174), "Wechsler Intelligence Scale for Children-Third Edition" (WISC-III) and WISC-IV (N = 239), "Wechsler Adult Intelligence Scale-Revised" (WAIS-R) and WAIS-III (N = 191), and WAIS-III and WAIS-IV ( N = 240). Second, equal percentile equating was applied to each of the samples independently. Although the two methods produced different patterns of results, both methods showed some evidence of variation in the magnitude of the Flynn effect across ability levels. These results call into question the practice of adjusting IQs based on an average expected Flynn effect in routine clinical evaluations. (Contains 3 tables and 6 figures.)