Abstract Several tetrazole derivatives have been prepared from 7‐amino‐2‐hydroxy‐3‐phenyl‐1,8‐naphthyridine (Id). Evidence is presented to demonstrate that the tetrazole ring structure is the dominant species in the solid state and in alkaline solution while the open‐chain azido form dominates in acidic solution. In addition it has been shown that the presence of a phenyl group in a position adjacent to the tetrazole nucleus apparently stabilizes the tetrazole ring.