Following the publication of Maxfield's results in the treatment of radiation sickness by pyridoxine hydrochloride (vitamin B6) in 1943 (6), we became interested in this drug and subsequently began its use in radiation sickness at The Henry Ford Hospital. In order to give the drug a thorough trial, it was decided to limit its use to the more severe cases and not to use it prophylactically. With this in view, we arbitrarily classified our cases of radiation sickness into four groups: (1) mild (anorexia and some nausea); (2) moderate (rather severe nausea, distaste for food, and occasional vomiting); (3) severe (pronounced nausea and frequent vomiting); (4) late or inflammatory symptoms due to proctitis, enteritis, and cystitis. No medication was offered to patients falling in the first group. Those in the other three groups received intravenous injections of 25 to 50 mg. of pyridoxine hydrochloride, in the form of Hexabetalin, beginning with the onset of symptoms. No other medication was given to any patient either prophylactically or otherwise unless specifically indicated. The injections were made at intervals varying from one to four days according to therapeutic response. The results were arbitrarily classified as: (1) excellent, i.e., complete relief of all symptoms; (2) good, i.e., relief of all vomiting and most of the nausea; (3) poor, i.e., no appreciable abatement of symptoms. Since inauguration of the use of pyridoxine hydrochloride, 81 patients have received this drug. The age and sex of the patients, the diagnosis, daily total x-ray dosage, and results of medication are given in the accompanying tabulation. Fractional doses to skin tolerance were used in most cases, and the total daily dosage represents the total roentgens, measured in air, given to all fields treated. From the accompanying table it is seen that, among the total of 81 cases, excellent results were obtained in 44 (54 percent), and good results in 28 (35 per cent). In 9 cases (11 per cent) vomiting was not entirely relieved and a troublesome degree of nausea remained. Some of the last group had a noticeable relief of symptoms, and others none at all; in general, there was no relief of diarrhea, tenesmus, and urinary frequency, but in many cases nausea and vomiting were diminished. Tincture of opium in a suitable vehicle gave the greatest relief to the Group 4 cases. Recent literature has added to the possible physiological causes of radiation sickness. Bean, Spies, and Vilter (1) gave x-ray therapy to patients who had a definite vitamin deficiency and who were suffering from various stages of pellagra or peripheral neuritis. They found a known, although rough, correlation between the severity of radiation sickness and the degree of vitamin deficiency. They were also able to show that correction of the vitamin deficiency prior to x-ray therapy was much more efficient in obviating radiation sickness than administration of vitamin B after irradiation was begun.