The aim of this paper was to evaluate the long-term (5 years) efficacy of nasal salmon calcitonin in prevention of trabecular postmenopausal bone loss, which was a follow-up of a previously published study (3 years); a randomized, controlled group comparison. One hundred healthy postmenopausal women were randomly chosen from those (186) having completed the 3 year protocol. The 100 women were allocated to an additional 2 year period (total of 5 years) of treatment with either 500 mg d-1, 5 days week-1 of calcium or the same amount of calcium plus 50 IU d-1, 5 days per week of nasal salmon calcitonin, 87 (87%) women complied with the protocol throughout. The main outcome measures were the bone mineral density of the lumbar spine (1-BMD) (DPA) and biochemical parameters reflecting bone turnover (serum alkaline phosphatases, urinary calcium/creatinine and hydroxyproline/creatinine ratios). The women receiving calcium alone presented a significant decrease in 1-BMD after 6 months [-1.6 (0.5)%] [mean(SEM)] (P < 0.01) and this decrease remained significant after 36 months [-6.1(0.8)%] (P < 0.01) and until the end of the trial [-6.6(1.0)% at t60] (P < 0.01). In women receiving calcium and calcitonin, 1-BMD significantly increased after 36 months [+2(0.7%] (P < 0.01) and 42 months [+2.5(0.7)%] (P < 0.01 and was unchanged at the other times of investigation [+1.1 (1.1)% at t60] (NS). The evolution of BMD in the two groups was highly significantly different (P < 0.001) since the sixth month of the study and remained so until the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)