Flash-photolysis experiments carried out with deuterated thiazole and oxazole confirmed that the carrier responsible for the bands in the region 2500 − 3050 Â, reported earlier by us in the flash-photolysis of isoxazole, oxazole and thiazole, contains only one hydrogen atom. It is also found that the progression-forming frequency of 1005 cm−1does not involve the motion of the hydrogen atom. The assignment of the carrier to HNC has been considered in the light of the recent theoretical work on this molecule.