The results are displayed in F1. There were 13 subjects with the met/met COMT genotype, 31 with the met/val genotype, and 29 with the val/val genotype, a distribution consistent with Hardy-Weinberg expectations (χ2=0.84, df=2, p=0.67). The mean number of categories completed by the 73 subjects was 5.48 (SD=1.28), and there was no significant difference (F=1.44, df=2, 70, p=0.25) between the three genotypic groups. The mean number of perseverative errors for the subjects with the met/met genotype was 7.46 (SD=4.01), for met/val it was 13.03 (SD=11.18), and for val/val it was 12.21 (SD=9.08). ANOVA revealed a significant relationship between COMT Val158Met genotype and the number of perseverative errors (F=4.43, df=2, 70, p=0.02). The met/met group committed significantly fewer perseverative errors than either the met/val group (t=2.43, df=70, p=0.02) or the val/val group (t=2.35, df=70, p=0.02). There was no significant difference between the performances of the met/val and val/val groups (t=0.31, df=70, p=0.75). No significant differences were observed between the three genotypic groups in age (F=0.03, df=2, 70, p=0.97), sex (χ2=4.67, df=2, p=0.10), or ethnicity (Fisher’s exact test, p=0.18).