Osteopenia and osteoporosis are being described more frequently in people with HIV infection. This study will test the efficacy of alendronate in comparison with a placebo after 2 years, in people with primary osteoporosis. People will receive the recommended adequate intake of calcium and vitamin D.

The purposes of this trial are:

• To study the efficacy of alendronate in HIV-associated osteoporosis
• To measure the prevalence of osteoporosis in HIV patients and to detect risk factors in a large cohort of HIV patients from the screening phase

Inclusion Criteria:

• Non-pregnant
• Non menopausal women
• Total femur BMD below -2.5 SD (T score) or lumbar spine BMD below -2.5 SD (T score) or BMD below -1 associated with a vertebral osteoporotic fracture (diminution of vertebral height over 20%)
• HIV infection known for at least 5 years
• CD4 cell count over 50/mm3
• Karnofsky score over or equal to 70
• Written informed consent.

Exclusion Criteria:

• Osteoporosis resulting from a cause other than HIV: vitamin D deficiency (in that case, after receiving high-dose calcium and vitamin D for 1 month, patients will be randomized without a new screening), renal failure, heart failure (NHYA class III or IV), treatment with glucocorticoid at a dose over or equal to 0.5mg/kg/d for 15 days or more at time of inclusion or during the previous 6 months; thyroid or other endocrine disease if untreated for more than 6 months; hypercalciuria
• Testosterone below normal if treatment is hormonal
• BMI below or equal to 18
• Severe lung failure
• Chronic alcohol intoxication
• Ongoing opportunistic infection
• Gastric ulcer of disease interfering with oesophageal motility in the previous 3 months
• History of treatment for osteoporosis
• History of malignancy in the previous 5 years (except skin cancer and Kaposi)
• Cytotoxic chemotherapy or cytokine therapy
• Liver cirrhosis
• Breast feeding