[1-14C]Docosahexaenoic acid (n-3) was incubated at 37 degrees C for 30 min in the presence of rat liver microsomes and 1 mM NADPH. The products were isolated using organic solvent extractions, reverse phase, and normal phase high performance liquid chromatography. Isolates were identified using ultraviolet spectroscopy, capillary gas-liquid chromatography, and gas chromatography-mass spectrometry. The major metabolites were: 19,20-, 16,17-, 13,14-, 10,11-, and 7,8-dihydroxydocosapentaenoic acids, 22-hydroxydocosahexaenoic acid, and 21-hydroxydocosahexaenoic acid. The minor metabolites were 17-hydroxy-4,7,10,13,15,19-, 16-hydroxy-4,7,10,17,19-, 14-hydroxy-4,7,10,12,-16,19-, 13-hydroxy-4,7,10,14,16,19-, 11-hydroxy-4,7,9,13,16,19-, 10-hydroxy-4,7, 11,13,16,19-, 8-hydroxy-4,6,10,13,16,19-, and 7-hydroxy-4,8,10,13,16,19 -docosahexaenoic acids. These metabolites of docosahexaenoic acid resulted from four distinct classes of oxidation, omega-hydroxylations, (omega-1)-hydroxylations, epoxidations, and lipoxygenase-like hydroxylations. The similarity of these product profiles to those reported for comparable microsomal incubations with other essential fatty acids suggest that microsome cytochrome P-450 monooxygenases were involved.