Thirty anthropometric measurements were analyzed in 147 adults with Martin-Bell syndrome (MBS) (56 men and 91 women) and in a random sample of 108 normal women and 111 men. Results of the univariate comparison of the age, height, or weight-adjusted variables between MBS and normal individuals of either sex indicated that a decrease in stature, in upper limb length, and in upper face height, and an increase in jaw length, chest circumference, and waist width occurred in both affected men and in heterozygous women. While the increase in ear height and breadth and in hypermobility of finger joints and decrease in palm width and bigonial diameter occurred only in affected men, increased bispinal and bitrochanteric diameters, upper arm circumference, and palm and wrist widths were characteristic deviations in heterozygous women. Multivariate analysis in the form of principal components showed some differences in the pattern of interrelationships in individual measures between MBS and normal individuals. In particular, and in contrast with both normal groups, height and weight tended to load on separate components (as did head and midfacial measures) in MBS individuals. A discriminant function based on all body measurements included in this study resulted in almost complete separation of discriminant scores of normal from those of MBS men and in good separation of the scores from normal and heterozygous women. Classification rates based on these functions were from 95% in men to 85% in women. These already high classification rates may be further improved mainly by enlarging the samples and including some other category of traits such as dermatoglyphic measurements.