A double-blind, placebo-controlled, randomized, prospective two-center study was carried out to assess the effects of tibolone + fluoride versus placebo + fluoride therapy on trabecular and cortical bone in postmenopausal osteoporotic women. Ninety-four subjects (mean age 61.1 years, postmenopausal 13.5 years on average) with low bone mineral density (BMD) at baseline were randomized to 2.5 mg of tibolone (Org OD 14, Livial) plus 26.4 mg of fluoride (Fluocalcic) or placebo plus 26.4 mg of fluoride daily over 2 years; 55 (58.5%) subjects completed the study, the main reason for discontinuation being untoward gastrointestinal effects. BMD at the lumbar spine was measured by both dual photon absorptiometry (DPA) and dual-energy X-ray absorptiometry (DXA), and at the hip by DXA at 6-month intervals. Baseline values (DXA, g/cm2) for tibolone + fluoride and placebo + fluoride groups were 0.733 and 0.744 for the lumbar spine, and 0.761 and 0.788 for the hip. Change from baseline and percentage change from baseline were calculated for the intent-to-treat and completers groups. An analysis of variance (ANOVA) model or Wilcoxon test was used for statistical evaluation. There was a mean increase in BMD at the lumbar spine measured by DPA of 25.3% and 12.3% in tibolone + fluoride and placebo + fluoride groups, respectively (p = 0.01); with DXA, respective changes were 32.6% and 14.0% (p = 0.013). Data on BMD at the hip showed mean increases of 7.9% and 2.6% for the tibolone + fluoride and placebo + fluoride groups, respectively. We conclude that combined tibolone + fluoride treatment induces a highly significant increase in BMD at the lumbar spine without simultaneous loss of the cortical bone allowing for a meaningful reduction of the fluoride dose when given in combination with tibolone.