Bovine epitheloid lens cells can be kept in culture for almost one year. During subculturing a gradual process of cell elongation is observed. Using several techniques, including immuno-fluorescence with antibodies against actin, electron microscopy, two-dimensional gel electro-phoresis, drug treatment and measurement of actin polymerization by DNase I inhibition, it is shown that microfilament assembly parallels the process of cell elongation.