The purposes of this study were twofold: (1) to describe the growth of metacarpal bone dimensions in a large sample (n = 819) of Flemish girls, 12–18 years, and (2) to investigate the relationship among cortical bone dimensions, biological maturation, and participation in sports activities. Besides body mass and stature, Tanner-Whitehouse skeletal age (SA) was estimated and menarcheal status was assessed. Second metacarpal bone dimensions were measured on radiographs. Sports participation was determined by a standardized questionnaire. Results show that whereas medullary diameter decreased, all other second metacarpal dimensions increased significantly with age. When the girls were divided into five subgroups by SA, significant differences were found for metacarpal bone dimensions among the groups. Analysis of covariance revealed that skeletal maturity significantly differentiated for medullary diameter, cortical thickness, cortical area, and percent cortical area, even when chronological age, body mass, and stature were partialled out. However, no differences were found between contrasting SA groups for metacarpal length and periosteal diameter when chronological age, body mass, and stature were held constant. The metacarpals of postmenarcheal girls are ∼4% longer and ∼7% wider, and had ∼14% more bone area than age-matched, premenarcheal peers. No differences were found in periosteal diameter between pre- and postmenarcheal 14–15-year-old girls. Finally, sports participation was not associated with cortical bone in this group of healthy females (−0.16 ≤ r ≤ 0.17). © 1994 Wiley-Liss, Inc.