Metal complexes of 2-aminopyridine N-oxide (Hapo) have been characterised by infrared spectra, X-ray powder diffraction spectra, and by magnetic measurements and electronic spectra to liquid nitrogen temperature. Neutral Hapo appears to be an O-donor ligand in almost every case, according to spectroscopic evidence. The [M(Hapo) 6]X 2] complexes (M = Mn, Co and Ni; X drawn from ClO 4, BF 4 and NO 3) are octahedrally coordinated and [Cu(Hapo) 4](BFA 4) 2 is square planar. The complexes Co(Hapo) 2Br 2·C 2H 5OH, Ni(Hapo) 2Br 2, Cu(Hapo) 2(NO 3) 2, and the copper(II) halide complexes, are all antiferromagnetic and N-oxide bridged. Such bridging pyridine N-oxide, whilst common with copper(II), is rare with cobalt(II) and nickel(II). The temperature dependence of the magnetism of Ni(Hapo) 2Br 2 has been compared to that for various models. Other Hapo complexes with cobalt(II) and nickel(II) halides appear to be halide-bridged. Some previously reported complexes with pyridine N-oxide (po), of the type M(po)Hal 2·H 2O (M = Co, Ni), have been more fully characterised and are halide-bridged. The complexes [Fe(Hapo) 4Cl 2]Cl and [(Cr(Hapo) 4Cl 2]Cl·H 2O have trans-MO 4Cl 2 coordination. The complex Cu(apo) 2 contains deprotonated O,N-bonded ligand. The complexes Cu(apo) 2, [Cu(Hapo) 4](BF 4) 2, Cu(Hapo) 2(NO 3) 2 and the metal perchlorate complexes have been previously reported, the remaining complexes are new.