A retrospective study of bone mineral density (BMD) changes was performed in 53 osteoporotic women prior to carrying out a prospective study. Comparisons between BMD of controls (n = 16) and treated groups over a 14-22 month period showed that fluoride (n = 10) induced a significant (P < 0.05) increase in vertebral and a slight decrease in femoral BMD, whereas silicon (n = 8) induced a significant (P < 0.05) increase in femoral BMD. Etidronate (n = 13) and, to a lesser extent, magnesium (n = 6), induced a slight although statistically non-significant increase in vertebral BMD.