Cells grew out in tissue culture from 37 of 53 fibrocellular epiretinal membrane explants, those from membranes of less than four months' clinical duration growing more consistently, more rapidly, and more exuberantly than those from membranes of more than four months' clinical duration. Electron microscopy demonstrated prominent microfilaments in the cytoplasm of some of the cells, and immunostaining for actin showed great variations in the pattern and intensity of staining. An ATP contraction assay conducted on 44 detergent-extracted cells and 47 intact cells revealed in each case a 30% average reduction in cell area. Immunostaining for cytokeratins following the ATP assay showed no significant difference in cell contraction between epithelial cells and non-epithelial cells. Clinical duration of the membrane had no significant influence on the contractility of cells growing from the explant.