Abstract The crystal structure of cytochrome P-450cam complexed with the enantiomer (1S)-camphor has been solved to 1.8 Å resolution and compared with the structure of the (1R)-camphor P-450cam complex. The overall protein structure is the same for both enantiomer complexes. However, the orientation of the substrates in the heme pocket differs. In contrast to (1R)-camphor, the (1S)-enantiomer binds in at least two orientations. The major binding mode of (1S)-camphor resembles the one of the (1R)-enantiomer in that there is a hydrogen bond between Tyr-96 and the quinone group of camphor, and the 10-methyl group points towards the I-helix. The binding differs in that C-5 is not at a position suitable for hydroxylation. In the other orientation (1S)-camphor is not hydrogen bonded, but C-5 is located suitably for hydroxylation.