Studies on the catalytic reduction of nitrite on carbon electrodes modified with Co(II) tetra-2,3-pyridinoporphyrazine (CoTppa, 1), N,N',N ",N'''-tetramethyltetra-2,3-pyridinoporphyrazine ([CoTm-2,3-tppa](4+), 2) and Co(II) N,N',N ",N'''-tetramethyltetra-3,4-pyridinoporphyrazine ([CoTm-3,4-tppa](4+), 3) are reported. There is a close correspondence between the proximity of the methyl groups to the porphyrazine ring and the catalytic activity of the porphyrazine complexes. Bulk electrolysis gave ammonia and hydroxylamine as some of the products. The catalytic activity of the cationic complex, 3, towards the detection of low concentrations of nitrite (<10(-9) M) in water containing sodium sulfate, was compared with the activities of the anionic cobalt(II) tetrasulfophthalocyanine ([CoTSPc](4-), 4) and the mixed [(CoTm)-Tm-II-3,4-tppa](4+).[CoTSPc](4-) (5) complexes. Complex 5 showed the best catalytic activity of the three in that large currents were obtained for very low concentrations of nitrite.