Oral contraceptives consumption has been identified as a usual strategy for birth control among athletes. Nevertheless, its impact on body composition and sports performance remains unknown due to the heterogeneity in the formulation of these products and individual factors such as the menstrual cycle, age or sports discipline. PURPOSE: The aim of this study was to evaluate the effect of oral-contraceptive use on strength and body composition changes in trained women undergoing regimented resistance training (RT). METHODS: Twenty-three resistance-trained women (age 27.4±3.4 years; height 162.7±6.1 cm; body weight 60.5±7.8 kg; BMI 22.9±2.7 kg∙m-2) were randomized to either a non-oral contraceptive (n=11, NOC) or an oral contraceptive (n= 12, OC) group. After a 3-week familiarization period, all participants performed four sessions of RT per week over the course of an 8-week non-linear program. Dual X-ray absorptiometry was used to measure lean body mass and fat mass. Muscle power was measured by the countermovement jump (CMJ) test using a jump contact mat, and maximal strength was assessed by the one-repetition maximum (1RM) test in the back squat (SQ) and bench press (BP). RESULTS: OC significantly increased lean body mass [1.4±1.4(CI: 0.5, 2.3) kg; p= 0.007]; however, no changes were observed in the NOC group [0.7±1.1(-0.2, 1.5) kg; p= 0.0741]. No significant changes were seen in regard to fat mass in both OC [0.4±1.8(-0.7, 1.5) kg; p=0.437] and NOC [0.3±0.8(-0.2, 1.0) kg; p= 0.220]. Both OC and NOC increased upper-body 1RM [6.7±3.6(4.4, 8.9) kg; p<0.01] and [4.8±1.8(3.4, 6.1) kg; p<0.01], respectively; likewise, increased lower-body 1RM [11.9± 6.7 (7.7, 16.2) kg; p< 0.01] and [15.6±5.4 (11.7, 19.4) kg; p< 0.01], respectively. No significant changes were found in CMJ in both OC and NOC [0.7±1.1 (-0.1, 1.6) cm; p= 0.911] and [0.7±1.1(-0.1, 1.6) cm; p= 0.69], respectively. CONCLUSIONS: OC use in conjunction with RT produces similar increases in measures of strength and power compared to NOC in trained women and has potentially beneficial effects on lean body mass. Supported by University of Málaga (Campus of International Excellence Andalucía Tech).