In the course of screening for new antimetabolites from actinomycetes, strain KM-10329 was found to produce L-1,2,4-triazole-3-alanine. Many synthetic compounds containing the 1H-1,2,4-triazole ring are known, however, their natural occurrence has never previously been reported. The isolation, purification and structural identification of the compound were described. The structure was determined as L-1,2,4-triazole-3-alanine by spectral analyses (¹H NMR, ¹³C NMR, IR, MS), comparison with authentic D,L-1,2,4-triazole-3-alanine, and examination of specific optical rotation and CD spectrum. This is the first report of the natural occurrence of a compound containing the 1,2,4-triazole ring. The strain was also found to co-produce a proline antagonist, nourseimycin, which contains an unusual amino acid.