The kinetics of CO binding to P450 were analyzed using the Maximum Entropy Method. This analysis yields kinetic distribution profiles that correspond to P450 conformational landscapes. The results show that P450 1A1 and 3A4 structures are best defined as distributions of two or three conformers. Addition of substrate modified the distributions. In contrast, a flexible conformation was observed for the alcohol inducible and carcinogen metabolizing P450 2E1. The results suggest that the conformation of this P450 switches during the catalytic cycle, allowing for oxidative uncoupling and production of reactive oxygen species.