Compound N-methyl-2-(5-methyl-4-imidazolyl)ethylamine (5-methyl-N-methylhistamine) was submitted to a thorough pharmacological examination and was found to be a potent stimulant of H2 receptors, devoid of any appreciable effect on H1 receptors. Because of its high degree of specificity it therefore seems to represent an interesting drug to be used in clinical gastric secretory tests and an useful tool for the study of histamine H2 receptors.