Some hyperfine shifted 1 H resonances of 1-methylimidazole complex of horse ferricytochrome c (1-MeIm.cyt c) have been assigned for the first time using 1D saturation transfer and 2D EXSY exchange correlated spectroscopy) experiments. Kinetic and equilibrium data for 1-MeIm binding to cyt c at a temperature range of 303-319 K have been determined at pH 7.0 by using the NMR method. The observed thermodynamic parameters for 1-MeIm binding are ΔH o = 39.5 kJ.mol - 1 , ΔS o = 154 J.mol - 1 .K - 1 , and Ea = 142 kJ.mol - 1 . The source of the asymmetric spin density distribution in heme groups of 1-MeIm.cyt c and the reason of low affinity of cytochrome c for 1-MeIm are also discussed.