The competition kinetics between metal complexes and (NO)-N-. for aliphatic radicals is a convenient technique for determining the rate constants of the reactions of (NO)-N-. with aliphatic radicals. Thus, the rate constants of (CH3)-C-. and (CH2OH)-C-. with (NO)-N-. were determined to be (3.4 +/- 1.1) x 10(9) and (5.9 +/- 0.5) x 10(9) M-1 s(-1), respectively. The same rate constants can be determined, in several systems, from the decrease in the half-life of transient complexes with metal-carbon sigma-bonds which decompose homolytically. In the presence of (NO)-N-., the half-life of these transient complexes decreases, and their decomposition turns from second-order to first-order processes. From the dependence of the observed first order rate constant on (NO)-N-. and on the metal complex concentrations, it is concluded that the mechanism of the decomposition of these transients in the presence of (NO)-N-. involves the reaction of (NO)-N-. with the carbon-centered radicals as well as with the transient with the metal-carbon sigma-bonds to form the same products. The rate constants of the reactions of (NO)-N-. with (cyclam)(H2O)(NiCH32+)-C-III and (nta)(CoCH2OH)-C-III(H2O)(-) were determined to be (1.5 +/- 0.2) x 10(5) and (3.6 +/- 0.4) x 10(8) M-1 s(-1), respectively. The reactions of (NO)-N-. with complexes with metal-carbon a-bonds are analogous to those of aliphatic radicals and dioxygen with the same complexes. This is not surprising as (NO)-N-. is a radical. The biological implications of these results are discussed.