The free and total vitamin B_<12> contents in serum were observed on 62 normal subjects ranging in age from to 85 years. The total vitamin B_<12> content was found to decline slightly as the age advanced in both sexes. But the free vitamin B_<12> content showed no significient variations associated with age and sex. No sex difference in the vitamin B_<12> content, both free and total, was noticed in all the subjects.
