6-Oxo-prostaglandin F 1a (6-oxo-PGF 1a), derivatized by methylation, methoxylation and silylation, emerged from OV-1 and OV-17 silicone gas-liquid chromatographic columns as one major peak (equivalent chain length = 25.1). A standardization curve, constructed using pure 6-oxo-PGF 1a enable quantification down to 5 ng. Silicic acid column chromatography effectively separated 6-oxo-PGF 1a (free acid) from all other major prostaglandins. On thin-layer chromatographic silica gel plates, 6-oxo-PGF 1a was resolved as discrete spots, well separated from other prostaglandins when developed in 5 out of 7 solvent mixtures. The difference in rate of resolution between 6-oxo-PGF 1a and the PGFs in the various solvents afforded another criterion for identification. 6-Oxo-PGF 1a produced a distinctive yellow chromogen on thin-layer chromatographic silica gel plates sprayed with an anis-aldehyde-sulphuric acid reagent; the colour reaction is specific to 6-oxo-PGF 1a and some structurally related prostaglandins.