Thin-layer chromatographic (t.l.c.) analysis of the products formed from the incubation of an acetone-pentane powder of sheep vesicular gland microsomes with 7,10,13,16-docosatetraenoic acid (adrenic acid) revealed the presence of two products having Rf values identical to PGE2 and PGF2alpha. These products were purified by t.l.c., derivatized by treatment with methoxyamine, diazomethane, and N,O-bis-(trimethylsily1)-trifluoroacetamide, and these derivatives used for gas chromatography and gas chromatography-mass spectrometry. The results were consistent with 1a, 1b-dihomo-PGF2 and 1a, 1b-dihomo-PGF2alpha proposed structures. Formation of 1a, 1b-dihomo-PGF2 alpha could be increased, at the expense of 1a, 1b-dihomo-PGE2 by the addition of copper and reduced glutathione to the incubation mixture. Reduction of 1a, 1b-dihomo-PGE2 with NaBH4 in methanol resulted in total conversion to two products having chemical and physical properties consistent with 1a, 1b-dihomo-PGF2alpha and 1a, 1b-dihomo-PGF2beta proposed structures. The initial rate of adrenic acid-dependent oxygen uptake was determined to be 25% of that of arachidonic acid. The prostaglandin synthetase inhibitors, naproxen and 5,8,11,14-eicosatetraynoic acid (Ro 3-1428) inhibited adrenic acid-dependent oxygen uptake; Ro 3-1428 was shown to be a time-dependent inhibitor.