Multiple sclerosis (MS) may be associated with reduced bone mass and higher frequency of osteoporosis. Femoral and spinal bone mineral density (BMD) in 70 ambulatory MS patients (46 females and 24 males) was compared with 100 sex-, age-, and BMI-matched control individuals. BMD was reduced in male patients (lumbar spine 0.976 ± 0.114 g/cm(2) compared with 1.059 ± 0.147 g/cm(2) in controls, p = 0.024, total hip 0.946 ± 0.136 g/cm(2) compared to 1.036 ± 0.118 g/cm(2) in controls, p = 0.008, femoral neck 0.812 ± 0.136 g/cm(2) compared with 0.887 ± 0.135 g/cm(2) in controls p = 0.042), and only in the total hip in female patients (0.88 ± 0.127 g/cm(2) compared with 0.935 ± 0.112 g/cm(2) in controls, p = 0.018). Multivariate analysis demonstrated that the predominantly affected site was the hip. MS patients exhibit increased frequency of low bone mass compared with controls. Further studies should assess the etiologic factors and employ appropriate therapies.