In an attempt to obtain in vitro experimental models for sarcoidosis, the primary cultures of granuloma cells were initiated with lymph nodes from 10 sarcoidosis patients. The cells migrating from tissue expiants became confluent at 2 wk of culture. These cells exhibited overall morphologic features and enzymatic activities resembling those of in vivo granuloma epithelioid cells. By light and electron microscopy, the epithelioid cell in vitro contained a clear, large nucleus with 1 or 2 prominent nucleoli. The cytoplasm was characterized by the occurrence of lysosomal dense bodies and electron-lucent vacuoles, besides many mitochondria and well-developed Golgi complexes. The cell surface exhibited many processes, mainly lamellipodia. Large amounts of angiotensin converting enzyme activity (3.9 to 50.1 nmol/min/ml) and lysozyme activity (3.9 to 23.0 µg/ml) were demonstrated in the medium used for culture. The results indicated that the major cell population grown in these cultures is derived from the epithelioid cells in sarcoid granulomas.