There has been an ongoing interest in the reactions of nitric oxide (NO) with heme model compounds, with the goal of interpreting related reactions occurring in biology. With recent evidence that higher oxides (NO2-, *NO2, N2O3, etc.) may also be formed under bioregulatory conditions, there is a need to understand the reactivities of these compounds with such models. This review discusses the mechanistic studies of the reactions of iron, ruthenium, and osmium metalloporphyrin complexes with NO and the higher nitrogen oxides.