White rats kept on the B12-deficient diet for 9 weeks developed hyperchromic anemia, manifested the reduced content of cobalamines in the blood, kidneys, liver, myocardium and urine, the increased excretion of methylmalonic acid (MMA) and the intensified activity of CoA and its precursors participating in the reaction of acetylation in the liver, kidneys and myocardium. There was a decrease in the content of cobalamine-protein complexes that break down to the greatest extent at 80 degrees C. Ten-fold administration of cyanocobalamine (0.5 microgram/kg), calcium pantothenate (3.3 mg/kg) or of both the preparations concurrently removed the aforesaid disorders of cobalamine metabolism, with the most complete therapeutic effect being attained upon combined use of the vitamin preparations. Administration of pantothenate increased the content of cobalamines and cobalamine-protein complexes in the liver and myocardium, normalizing methylmalonylaciduria.