The purpose of this retrospective study was to compare the effects of long-term treatment (5 years) with elcatonin and alfacalcidol on bone mineral density (BMD) and the incidence of vertebral fractures in postmenopausal women with osteoporosis. Fifty-six osteoporotic women, more than 5 years after menopause and 58-79 years of age, were enrolled in the study and allocated to an elcatonin treatment group (20 units IM, weekly; n = 30) or an alfacalcidol treatment group (1 micro g/day, daily; n = 26). BMD of the lumbar spine (L2-L4) was measured by dual energy X-ray absorptiometry at baseline and every year for 5 years. There were no significant differences in age, body mass index, years since menopause, BMD, or number of prevalent vertebral fractures at baseline between the two groups. One-way analysis of variance with repeated measurements showed no significant longitudinal changes in BMD in either group, suggesting that both treatments sustained the BMD over 5 years. Two-way analysis of variance with repeated measurements also showed no significant differences in longitudinal changes in BMD between the two groups, suggesting that the effects of the two treatments on BMD were similar. However, the number of incident vertebral fractures per patient was significantly lower in the alfacalcidol treatment group than in the elcatonin treatment group (0.80 +/- 1.19 and 2.08 +/- 2.73, respectively; P < 0.05). These findings indicate that both treatments appeared to sustain lumbar BMD similarly over a 5-year period in postmenopausal women with osteoporosis, but alfacalcidol treatment may be superior to elcatonin treatment regarding the incidence of vertebral fractures. Further study with prospective observations are needed to confirm the results of the present study.