The association between relative skeletal age and fat patterning was analyzed by using data from the Fels Longitudinal Study for boys at chronological ages 8 to 17 years. Fat patterning, as indicated by age-specific means for three skinfold thickness indices adjusted for weight/stature2, was peripheral between 8 to 12 years of chronological age but began to increase in a centripetal direction towards a generalized distribution after 13 years. From 14 to 17 years of chronological age, boys with advanced relative skeletal ages had more centripetal fat patterns, as indicated by the ratio subscapular/(subscapular+triceps) skinfolds, than did those with retarded skeletal ages. The mean annual increment in this ratio was significantly greaterfrom 13 to 14 years of chronological age in boys with advanced relative skeletal ages than in those with retarded relative skeletal ages. Fat pattern index scores at 17 years of chronological age, however, could not be predicted from relative skeletal ages at 7, 11, or 14 years after adjustment for baseline fat pattern index scores and weight/stature2. It was concluded that fat patterning, as quantified by the ratio indices used in this study, was associated only weakly with relative skeletal age in boys. Fat patterning may be associated more strongly with other indicators of relative maturity such as secondary sex characteristics in adolescent boys.