An anthropometric survey of 41 variables (weight, height, 10 linear, 4 breadth, 22 craniofacial, 2 skinfold, and testicular volume), including multivariate discriminant analysis, was undertaken on 110 mentally retarded males (39 with and 71 without the fra(X) syndrome). The mean Z scores of the fra(X) syndrome males fell between −2.00 and 8.38 for bizygomatic diameter and testicular volume, respectively, and the range of the mean Z scores of the non-fra(X) males was from −2.64 to 2.26 for hand breadth and testicular volume, respectively. There was a statistically significant difference (P < .05) between fra(X) and non-fra(X) males for 18 measurements (weight, height, 7 linear, 2 breadth, 5 craniofacial, 1 skinfold, and testicular volume), with the greater measurements (excluding bizygomatic diameter) found in fra(X) males. Sitting height, knee-buttock length, middle finger length, and hand length were negatively correlated (P < .05) with age, whereas bizygomatic diameter, ear length, and ear width were positively correlated (P < .05) with age and head circumference, head length, and outer canthal distance were positively correlated (P < .05) with fra(X) chromosome expression in the fra(X) males. Triceps and subscapular skinfold thicknesses were negatively correlated (P < .05) with age, whereas ankle breadth, ear length, ear width, and nose length were positively correlated (P < .05) in the non-fra(X) males. Discriminant analysis of 34 fra(X) and 71 non-fra(X) males resulted in a discriminant function based on 6 of 17 anthropometric variables and age. In the discriminant analysis, patients with the fra(X) syndrome were distinguished from mentally retarded males without the fra(X) syndrome at an overall correct classification rate of 97.1% in our sample. The 6 anthropometric variables in the discriminant function were the Z scores representing testicular volume, ear width, head breadth, bizygomatic diameter, hand breadth, and hand length. Additional research is needed to test the usefulness of these variables in screening mentally retarded males for the fra(X) syndrome.