The raw material of cyanocobalamin was tested for preparation of the "Cyanocobalamin Reference Standard (Control 951)". Analytical data obtained are as follows: loss on drying, 1.8%; infrared spectrum, the same as that of the JP Cyanocobalamin Reference Standard (Control 936); thin-layer chromatography, three impurities were detected; high-performance liquid chromatography (HPLC), eight to nine kinds of impurities were detected and the total amount of impurities was estimated to be 1.6 +/- 0.13% (n = 4); assay, 99.7% by spectrophotometry specified in the JP XII and 100.4% by HPLC, respectively. Based on the above results, the raw material was authorized as the JP Cyanocobalamin Reference Standard (Control 951).