A randomized blind prospective study was carried out to determine if an anabolic androgenic steroid with a high anabolic/androgenic ratio, Group A, (1/0.05) methenolone enanthate (me), compared to an anabolic/androgenic agent with a low anabolic/androgenic ratio, Group B, (1.0/1.0) testosterone propionate (tp), compared to a control, Group C, cottonseed oil (co), affected midhumeral osteotomy healing in 100 two-month-old female Wistar rats. The rats received 4 mg/kg me, 4 mg/kg te, and equal volumes of co weekly. The rats were sacrificed at 2, 4, and 6 weeks. The entire humerus with the healing osteotomy was carefully dissected until all soft tissue attachments were stripped. The healing callus was then subjected to (1) biochemical analysis (hexosamine, hydroxyproline, and calcium), (2) biomechanical testing (progressive distraction of the callus at 1 mm/min on an electrohydraulic materials test system, model 1331, Instron Corp, Canton, MA, and (3) histology. Results of the biochemical testing demonstrated that the percentage of calcium in the healing callus at 2 weeks in group B (tp) was 7.3 +/- 1.0, and this value was greater than that in group C (co), 4.8 +/- 1.6 (p greater than .01), and greater than that in group A (me), 5.6 +/- 0.6 (p greater than .01). At 4 weeks, the percentage of calcium in the callus in group B (tp) was 6.8 +/- 1.9, in group A (me) 7.3 +/- 3.7, and these values were both greater than that in group C (co), 3.9 +/- 2.2 (p greater than .02 and .01, respectively). At 6 weeks the percentage of calcium in the callus in group B (tp) was 11.7 +/- 3.9 and in group A (me) 12.7 +/- 3.9, and again these values were both greater than that in group C (co), 6.7 +/- 2.6 (p greater than .02 and .01, respectively). The remainder of the biochemical analysis, hexosamine and hydroxyproline content, did not show a statistical difference in groups A, B, and C at 2, 4, and 6 weeks. The biomechanical studies and histology also failed to show statistical differences between the three groups at 2, 4, and 6 weeks. The conclusion of this study is that an agent with a low androgenic activity does not increase calcium callus concentrations early in the course of fracture healing compared to an agent with higher androgenic activity. As healing progresses, both agents increase the concentration of calcium in osteotomy healing. The clinical significance of this study is that agents with low androgenic activities favorably influence osteotomy healing and may be clinically useful because they lack unwanted virilizing activity.