self-injury is a defining feature of lesch–nyhan disease (lnd) but does not occur in the less severely affected lesch–nyhan variants (lnv). the aim of this study was to quantify behavioral and emotional abnormalities in lnd and lnv. thirty-nine informants rated 22 patients with lnd (21 males, 1 female), 11 males with lnv, and 11 healthy controls (hc; 10 males, 1 female) using two well-validated rating scales. the age of patients with lnd ranged from 12 years 7 months to 38 years 3 months (mean 22y 11mo; sd 7y 8mo), whereas the age range of those with lnv was 12 years 9 months to 65 years (mean 30y 7mo; sd 15y 2mo), and the healthy controls were aged 12 years 4 months to 31 years 3 months (mean 17y 10mo; sd 5y 7mo). behavioral ratings were based on the child behavior checklist and the american association on mental retardation's adaptive behavior scale – residential and community, 2nd edition. statistical analyses revealed that patients with lnd showed severe self-injury together with problematic aggression, anxious-depressed symptoms, distractibility, motor stereotypes, and disturbing interpersonal behaviors. patients with lnv were rated as being intermediate between the hc and lnd groups on all behavior scales. although the lnv group did not differ from hcs on most scales, their reported attention problems were as severe as those found in lnd. we conclude that self-injurious and aggressive behaviors are nearly universal and that other behavioral abnormalities are common in lnd. although patients with lnv typically do not self-injure or display severe aggression, attention problems are common and a few patients demonstrate other behavioral anomalies.