The production and spatial organization of connective tissue components 1n ciliary muscle cell cultures was studied with immunohlsto-chemlcal and ultrastructural methods. Antibodies against collagen types IV and VI, flbronectln and laminin were used.Laminin stains as pericellular network surrounding Individual muscle cells. Type IV collagen shows positive cytoplasmic staining and only small fod of extracellular Immunofluorescence. Staining for type VI collagen and flbronectln 1s seen near the ends of the bipolar cells, while the lateral sides of the cells remain unstained.Electronmlcroscopy shows that cultured ciliary muscle cells are surrounded by an Incomplete basal lamina. In addition, bundles of 5–20 nm thick extracellular microfibrils are seen. The bundles are oriented parallel to the axis of the cells and are 1n close contact with the cell membrane 1n areas where membrane-bound dense bands are formed. Immunoelectronmlcroscopy Indicates that the bundles contain flbronectln and type VI collagen fibrils. While the flbronectln fibrils approach the cell membrane directly, type VI collagen fibrils are usually separated from the cell membrane by fine fibrinous material of different nature. Quality and spatial organization of the extracellular material 1n ciliary muscle cell cultures shows marked similarities with the extracellular matrix of ciliary muscle 1n situ.