While earlier studies suggest an association of hyperactivity with short stature and low birth weight, it is unclear if a specific association exists when contemporary diagnostic criteria are utilized, such as DSM-IV. The purpose of this study was to examine group differences in physical characteristics between children with ADHD and other developmental disorders. Children referred to a multidisciplinary evaluation clinic within a large, tertiary care hospital served as subjects. As part of the initial evaluation, the developmental pediatrician inquired about gestational age and birthweight, and measured height, weight, and head circumference. Measures were converted to percentiles using standardized tables and the percent ideal body weight was calculated on 262 children. The diagnostic evaluation included standardized behavior rating scales (e.g. Conners Parent Rating Scale), the age-appropriate Wechsler scale of intelligence, and a structured diagnostic interview conducted by a psychologist or psychiatrist. For the present study. children were stratified into 4 groups: ADHD Combined Type (n = 166), ADHD-Predominantly Inattentive Type (ADHD-PI)(n = 38), Anxiety/Mood Disorders(AM) (n = 14), and Cognitive Impaired (CI) (n = 44). The ADHD group had a mean height of 57%, weight 66%, percent ideal body weight ratio of 110, and mean head circumference of 65%. There were no significant group differences for any anthropometric measure. Percent-ideal body weight correlated with Conners Anxiety (r =.19, p <.001), Learning Problems (r =.16, p <.01), Conduct Problems (R =.13, p <.05), and inversely with Performance IQ (r = -.13, p<.5). Most children with ADHD were average or above average in stature. The results do not provide support for physical immaturity as a specific etiological factor for ADHD. Large stature is associated with anxiety, non-verbal learning problems, and behavior problems within the clinic-referred sample. However, only a small percentage of the variance is accounted for by anthropometic measures. Nonetheless, the percent ideal body weight may be an important measure related to the management of these disorders, and should be evaluated further in community-based as well as clinic-referred samples.