Introduction. Rapid bone loss and fractures occur early after solid organ transplantation. We examined the preliminary results of a prospective study evaluating the efficacy of prophylactic use of bisphosphonates in renal allograft recipients. Methods. Bone mineral density (BMD) was measured at the lumbar spine and the hip by dual energy X-ray absorptiometry at 1, 6, 12 months. Alendronian or risedronian were initiated for patients with osteopenia or osteoporosis at 1 month who had no contraindications to bisphosphonates. The treatment lasted at least 6 months. Sixty-six patients were included in the study; 39 were treated with bisphosphonates (A), and 27 were drug-free (B). Presently, 24 group A and 13 group B patients have completed the 12-month observation period. Results. In group A 53.8% (21) subjects had osteoporosis and 46.2% (18), osteopenia. Mean T-score L-2-L-4 in group A at 1, 6, and 12 months were: (-)2.22 +/- 1.06; (-)2.07 +/- 1.25; (-)1.89 +/- 1.07, respectively. The T-score increase between 6 and 12 months was significant (P = 0.0014). The relative rise in BMD L-2-L-4 between 1 and 12 months was 2.26%. In group B mean T-score L-2-L-4 at 1, 6, and 12 months were: (-)0.26 +/- 1.34; (-)0.80 +/- 1.19; (-)1.2 +/- 1.59, respectively. The T-score decrease between 1 and 12 month,; in group B was significant (P = .0082). The 12-month relative decrease in femoral neck and trochanter BMD in group B was (-)2.1% and (-)2.75%, respectively. Conclusion. Bisphosphonates are effective for prophylaxis of rapid bone loss early after renal transplantation.