Recent progress on the application of cytochrome P450 (P450) to bioconversion processes, biosensors, and bioremediation were reviewed. Because regio- and enantioselective hydroxylation makes chemical synthesis difficult, a bioconversion process using P450 would be quite attractive. One of the most successful industrial applications of P450 may be the bioconversion process for pravastatin formation using a Streptomyces carbophilus CYP105A3. Unfortunately, practical application of P450s in the bioconversion process is limited because of their low stability, low activity and co-factor dependency. However, directed evolution is expected to generate useful P450 biocatalysts for a wide range of substrates. Shunt pathways of CYP152A1, CYP152A2, and CYP152B1 are notably promising for practical application, because these P450s require neither reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) nor electron donor proteins, and efficiently catalyze using hydrogen peroxide. A P450 biosensor using biochip technology is expected to become a tool for rapidly determining drugs and endogenous substances in plasma at a low cost. Bioremediation of dioxins and polychlorinated biphenyls (PCBs) by the CYP1 family appears to be possible by using suicidal, genetically engineered microorganisms. The P450 superfamily has tremendous potential for practical applications in various fields.