Alkaline phosphatase (ALP) is an enzyme that is expressed in a variety of tissues. Among the isoforms of ALP, bone-specific alkaline phosphatase (BAP) is used as a marker for evaluating bone metabolism. We investigated the clinical usefulness of the ratio of serum BAP to total ALP for the diagnosis of various disorders in general practice. We retrospectively analyzed the cases of 107 Japanese patients whose serum BAP levels were exam-ined, focusing on clinical characteristics. We observed that the BAP/ALP ratios of the patients with fever and those with inflammatory diseases were significantly lower than the ratios of other patient groups. The BAP/ALP ratios of the patients with osteoporosis and those with metabolic bone diseases were higher than those of the patients with other conditions. The BAP/ALP ratio was found to be negatively correlated with age, a cor-relation that has not been found in other ethnicities. The serum BAP/ALP ratio was inversely correlated with serum CRP levels but was positively correlated with serum albumin levels and hemoglobin concentrations. Collectively, our results suggest that the BAP/ALP ratio could be a useful predictor for important geriatric con-ditions seen in general practice.