Osteoporosis (OP) is considered as one of the commonest metabolic bone diseases in orthopedics, characterized by a reduction in bone mass density and micro-architectural deterioration of bone tissue leading to diminished material properties with an increase in bone fragility and susceptibility to minor trauma fractures. The aim of this cross sectional study was to detect the level of vitamin D in patients suffering from primary osteoporosis and to correlate their levels with bone mass index. This work was performed - at the Orthopedic Outpatient Clinic of   King Abdul Aziz specialist Hospital, Taif, (KSA) - on 115 patients (77 females and 38 males) fulfilling WHO revised criteria of 1994 for osteoporosis. The mean age of patients was 67.5± 8.2. A medical history was taken and bony pains, fragility fractures, and loss of height, were elicited, with Inclusion criteria in the form of a T-score ≤ −2.5 SD at the lumbar spine, with exclusion of any patient with secondary osteoporosis. Full physical examination and investigations were done including estimation of serum total vitamin D and X-ray of lumbar and thoracic spine. Results indicate that  the mean total vitamin D and T-score were 19.7±6.6 ng/dl and -2.9± 0.4 respectively. 88.7% of osteoporotic cases were complaining of bone pains, 47% of them complaining of height loss and 47.8% of them had spine fracture in X-ray. Positive strong significant correlation between total vitamin D and T-score (r=0.83, p value <0.0001) was found. It could be concluded that there is a significant positive strong correlation between total vitamin D and bone mass index in primary osteoporotic patients in Taif - KSA.It is recommended that adequate intake of calcium and vitamin D during prophylaxis and treatment of osteoporosis is necessary.