In order to characterize proteins unique to organized epitheloid cells, proteins havebeen sequentially extracted form both foreign body and allergic granulomas in man at varoius times after intradermal injection of beryllium oxide suspension. Treitium-labeled l-tyrosine was injected intralesionally 2 weeks before excision of granulomas. Prolongedextraction with 8 m urea yeilded increases amounts of radioactivie protein form older (8-to 26-week) allergic granulomas but not from 4-to6-week-old or foreign body granulomas (consisting of mononuclear cells and phagocytes). Sephadex G-200 column chromatographyand sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the urea extractsfrom 8-week and older allergic granulomas revealed distinct readioactive protein peaks with molecular weights of approximately 172,000 to 208,000. Antisera raised to one of these proteins gave a precipitin line in agar gel diffusion with lines of identity againsturea extracts of several allergic granulomas but not against similiar extracts of foreignbody granulomas. The results suggest synthesis of distinctive high molecular weight proteins in allergic granulomas which may serve as "markers" for organized epitheloid cell granulomas as they transform from mononuclear cells.