The prompt antidotal effect of PAM (pyridine-2-aldoxime methiodide) in alkylphosphate poisoning was demonstrated in five cases here reported. The patients were all farm workers who had been spraying fields with parathion. Cholinesterase determinations in both serum and erythrocytes were carried out and clearly showed the inhibitory effect of the parathion upon the enzyme. Intravenous administration of PAM relieved some of the symptoms instantly, and cholinesterase determinations demonstrated the reactivation of the enzyme. PAM was effective after either oral or parenteral administration and could be given in adequate doses without disagreeable side-effects. It also relieved certain symptoms, such as muscular fasciculation, that are not relieved by atropine.