THE THREE amphetamine preparations in use are amphetamine sulphate, dextro-amphetamine sulphate, and d-N-methylamphetamine hydrochloride. The first is known as ' Benzedrine', the second as 'Dexedrine' and the third as , Methedrine' or ' Pervitin '.Although Phillips (1954) implies that the actions of the three preparations are identical, other writers disagree. Golla, Blackburn and Graham (1940) found, in 2 subjects, that the effect of 10 mg. of amphetamine sulphate equalled that of 5 mg. of methylamphetamine. Davidoff (1943) and Jackson (1946) reported that methylamphetamine showed a greater duration of effect than did amphetamine, and the first writer found that it produced more rapid results and gave greater motor activity in 8 normal and 8 depressed subjects. Myerson (1947) wrote that it produced a greater loquacity and Levine, Rinkel and Greenblatt (1948), investigating 75 patients, reached the conclusion that it had a greater central effect and a smaller peripheral, vascular effect than has amphetamine,