The efficacy of calcium (Ca) in reducing bone loss is debated. In a randomized placebo-controlled double-masked study, we investigated the effects of oral Ca supplements on femoral shaft (FS), femoral neck (FN) and lumbar spine (LS) bone mineral density (BMD), and on the incidence of vertebral fracture in vitamin-D-replete elderly. Ninety-three healthy subjects (72.1±0.6 years) were randomly allocated to three groups receiving 800 mg/day Ca in two different forms or a placebo for 18 months. Sixty-three patients (78.4±1.0 years) with a recent hip fracture were allocated to two groups receiving the two forms of Ca without placebo. FS BMD changes in Ca-supplemented non-fractured women were significantly different from those in the placebo group (+0.6±0.5% v –1.2±0.7%,p<0.05). there="" was="" no="" difference="" in="" effect="" between="" the="" two="" forms="" of="" ca.="" the="" changes="" of="" +0.7±0.8%="" v="" –1.7±1.6%="" in="" fn="" bmd="" of="" ca-supplemented="" women="" and="" the="" placebo="" group="" did="" not="" reach="" statistical="" significance.="" in="" fractured="" patients,="" fs,="" fn="" and="" ls="" bmd="" changes="" were="" –1.3±0.8,="" +0.3±1.6="" and="" +3.1±1.2%="">p<0.05 for="" the="" last).="" the="" rate="" of="" new="" vertebral="" fractures="" was="" 74.3="" and="" 106.2="" fractures="" per="" 1000="" patient-years="" in="" ca-supplemented="" non-fractured="" subjects="" and="" in="" the="" placebo="" group,="" respectively,="" and="" 144.0="" in="" ca-supplemented="" fractured="" patients.="" thus,="" oral="" ca="" supplements="" prevented="" a="" femoral="" bmd="" decrease="" and="" lowered="" vertebral="" fracture="" rate="" in="" the="">