OBJECTIVE: This study assessed the effects of different doses of all-trans retinoic acid on bone resistance by conducting a biomechanical flexion study on young rats' tibias. METHODS: Fifty-eight young rats were divided into four groups according to the all-trans retinoic acid content of their diets: control group (n=15), chow not enriched with all-trans retinoic acid; chow enriched with 0.3mg of all-trans retinoic acid per kilogram (n=13); chow enriched with 10mg of all-trans retinoic acid per kilogram (n=15); and chow enriched with 50mg of all-trans retinoic acid per kilogram (n-15). After 30 days of this diet, the animals were killed, their left paws were frozen and dissected and the tibias were submitted to the flexion study which assessed maximum force and shear modulus. One-way analysis of variance was used with significance set at p<0.05. RESULTS: The mean maximum force values in newtons (SD) were: control group =37.94, SD=4.76; 0.3mg group = 36.49, SD= 4.38; 10mg group = 40.12, SD=6.03; 50mg group =35.68, SD=5.22 (p=0.107). The mean shear modulus values (SD) in newtons/millimeter were: control group =31.84, SD=6.75; 0.3mg group =29.18, SD=4.35; 10mg group =35.48, SD=8.14; 50mg group =30.31, SD=7.14 (p=0.85). CONCLUSION: Biomechanical studies showed that different doses of all-trans retinoic acid for 30 days had no effect on young rats' bone resistance.