The air-stable title compound, C(12)H(13)N(3)O, which is of inter-est due to its anti-bacterial properties, is an almost planar mol-ecule in which the ten atoms forming the 1,8-naphthyridine ring have an r.m.s. deviation of 0.03 Å from the least-squares plane calculated using the ten atoms. The plane of the acetyl-amino group is slightly inclined [11.7 (2)°] to the plane of the 1,8-naphthyridine ring.