The synthesis of tetralabeled histidine 15 described. Glycine‐15N was converted essentially by literature procedures to 4‐chloromethylimidazole‐3‐15N‐2,5‐2H2. Alkylation of ethyl acetamidocyanoacetate‐2‐13C, followed by acid hydrolysis and decarboxylation yielded DL‐histidine‐α‐ 13C‐3‐15N‐2,5‐2H2. The compound is useful as a mass spectrometric standard for the measurement of histidine and metabolites in biological media.