For decades Vitamin B12 injections have been administered to patients with no documented deficiency. A previous study identified a cohort of patients who described vitamin B12-responsive symptoms despite lack of cobalamin deficiency as measured by conventional laboratory tests. These patients have been studied further and, when compared with controls, were found to have had more prescriptions for psychoactive drugs (P less than .001) and to have had more hospitalizations related to symptoms suggestive of neuropsychiatric problems (P less than .01). To confirm these findings and to determine national estimates for vitamin B12 use, an analysis of the 1985 National Ambulatory Medical Care Survey (NAMCS) was conducted. This analysis supports a significantly higher frequency of neuropsychiatric complaints among patients who received vitamin B12 injections (P less than .001). In addition, the NAMCS analysis indicates that of the calculated 2,516,564 vitamin B12 injections given in 1985, only 376,488 were for a diagnosis compatible with a cobalamin deficiency state (a 7:1 observed over expected ratio). According to the national data set analysis, vitamin B12 injections are given most frequently in the rural south by a doctor of osteopathy in solo practice.