Tapping mode atomic force microscopy was applied for a study of the molecular organization and aggregation states of purified bovine adrenocortical cytochrome P450scc present in thin solid films. The films of pure cytochrome P450scc or cytochrome P450scc mixed with lipids were transferred onto substrates of highly oriented pyrolytic graphite or mica. Images of the cytochrome P450scc films show that the topology of the proteins is drastically dependent on surface pressure. An effect of hemeprotein on the structural organization of lipid was observed. Images of the hemeprotein molecules and/or their aggregates provide a new insight for the further understanding of the nature of hemeprotein-hemeprotein and hemeprotein-lipid interactions as well as the membrane topology of cytochrome P450scc.