OBJECTIVE To evaluate the efficacy and safety of rhPTH (1-34) vs. elcatonin. METHODS Sixty patients with primary OP were randomly divided into two groups according to the ratio of 3:1. rhPTH (1-34) group (PTH group) was treated with subcutaneous injection of rhPTH (1-34) 20 μ g daily for 18 months, and the elcatonin group (CT group) was treated with intramuscular injection of elcatonin 20 U weekly for 12 months. Bone mineral density (BMD) of the lumbar spine 2-4 (L2-4) and femoral neck, serum calcium and phosphorus, urinary calcium, serum bone specific alkaline phosphatase (BSAP), and urinary c-terminal telopeptides of type I collagen/creatinine (uCTX-I/Cr) were tested at baseline, and 6, 12, and 18 months after treatment. RESULTS In PTH group, BMD of L2-4 at 6, 12, and 18 months, BDM of femoral neck at 18 month, BSAP at 6 and 12 months and uCTX- I/Cr at 6, 12 and 18 months were all significantly raised. In CT group, BMD of L2-4 at 12 month and that of femoral neck at 12 and 18 months were significantly elevated, while BSAP was significantly decreased at 12 and 18 months, and no significant difference on CTX- I/Cr was observed. When BMD growth and growth rate between two groups were compared, PTH group had better improvement in L2-4 BMD and growth rate than CT group at 6, 12, and 18 months. BMD growth and growth rate of femoral neck at 12 month and its growth at 18 month in CT group were higher than in PTH group, but there was no significant difference between two groups regarding the growth rates at 18 month. Besides, there were no significant differences regarding the rates of adverse reactions between two groups. CONCLUSIONS rhPTH (1-34), is safe and effective in the treatment of primary OP. It is superior to elcatonin in improving vertebral BMD at onset time, growth rate and growth range, but inferior to elcatonin at BMD of femoral neck.