We aimed to compare and evaluate the efficacies of a continuous regimen of intranasal salmon calcitonin (SCT) and two cyclic regimens (different cyclic regimens from previous studies) based on alternating 15 days or on 10 days consecutively per month for 1 year in the treatment of postmenopausal osteoporosis. We performed an open-label, prospective, randomized clinical trial. A total of 120 postmenopausal osteoporotic participants between 50 and 65 years old were randomly assigned to one of three treatment groups. Patients in group 1 (n=40) received continuously SCT nasal spray at a dose of 200 IU/day, plus continuously 500 mg/day elementary calcium and 0.25 mu g/day 1-alpha hydroxyvitamin D3, for 1 year. Patients in group 2 (n=40) received cyclically SCT nasal spray at a dose of 200 IU/day on alternating 15 days per month, plus continuously 500 mg/day elementary calcium and 0.25 mu g/day 1-alpha hydroxyvitamin D3, for 1 year. Patients in group 3 (n=40) received cyclically SCT nasal spray on 10 days consecutively per month (20 days/month rest), plus continuously 500 mg/day elementary calcium and 0.25 mu g/day 1-alpha hydroxyvitamin D3, for 1 year. Data was evaluated by repeated analysis of variance (ANOVA). In addition, statistical differences between groups were assessed by the two-tailed Student's t test. After 1 year of the study, seven patients from group 1, eight patients from group 2 and five patients from group 3 withdrew from the study. No patient discontinued the study because of adverse drug effects. There was a statistically-significant improvement in pain intensity VAS scores at the end of the year to baseline scores in all three groups (p < 0.001). There was no significant difference in pain intensity VAS scores between groups at the end of the year (p > 0.05). Lumbar and femur neck BMD scores improved significantly at the end of treatment in all three groups (p < 0.05). There was no statistically-significant difference in BMD scores between groups at final (p > 0.05). Urinary DPD/Cre levels decreased significantly in all three groups by the end of the year (p < 0.05). There was no statistically-significant difference in urinary DPD/Cre final levels between groups (p > 0.05). According to the results of the present study, consecutive 10 days therapy with SCT, which is the first in the literature to our knowledge, is as effective as the other two regimens in the treatmnent of osteoporosis. Both cyclic regimens in our study (alternating 15 days and 10 consecutive days each month for 1 year) do appear to offer some advantages, especially economically and clinically, as compared to continuous treatment.