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To estimate the biological maturity status of youth football players 9–14 yr old using a noninvasive method and to compare the body size of players of contrasting status.Subjects were members of youth football teams in two central Michigan communities. Height and weight were measured on 653 boys 8.7–14.6 yr. Heights of biological parents of 582 boys were reported and subsequently adjusted for overestimation. Decimal age, height, and weight of the player and midparent height were used to predict mature (adult) height for the boy. Current height of each player was expressed as a percentage of his predicted mature height to provide an estimate of biological maturity status. Percentage of predicted mature height of each boy was expressed as a z-score to classify players into maturity groups. ANCOVA, controlling for age, was used to compare body size in contrasting maturity groups.Mean percentages of predicted mature height of the players matched those of longitudinal reference samples, but there was a trend for higher percentages among older players, suggesting advanced maturation. Overall, 405 boys were classified as on time/average in maturity status (69.6% [95%CI 65.7–73.3]), 154 were classified as early/advanced (25.5% [95%CI 23.0–30.3]), and only 23 were classified as late/delayed (3.9% [95%CI 2.6–6.0]). The gradient for height, weight, and BMI was as follows: early > on time > late, and differences were greater for weight and the BMI than for height.Percentage of predicted mature height attained at a given age appears to be a reasonable indicator of maturity status. The method needs to be validated with other more direct indicators (skeletal age, sexual maturation) and applied to other samples.