The purpose of this study was to evaluate the immunohistochemical localization of prostaglandin E (PGE) in rat carrageenin granuloma, comparing with the quantitative contents of PGE determined by the radioimmunoassay in our previous study. The contents of PGE in the previous, quantitative study was the highest after 3 days of the carrageenin injection. Numerous macrophages were observed at that time and the most of them were intensely stained for PGE in this study. The number of macrophages, however, were markedly decreased and the staining intensity for PGE were almost inhibited in indomethacin-treated group. These results suggest that the intensity of immunohistochemical staining for PGE is correlated with the biochemical, quantitative result of PGE.