The aim of the study was to determine the influence of 48-day hypodynamic stress on the ultrastructure of the cortical layer cells of eye lens. Hypodynamic stress was induced in Chinchilla male rabbits (weight 2.5-3.0 kg; n=8) by placing them in metal hutches for 48 days. Rabbits (n=8) of the control group (non-stressed) were kept under normal vivarium conditions. Following the hypodynamic regime (after 48 days) the rabbits (stressed and control) were anaesthetized using thiopental sodium (35 mg/kg). On removing their eyes, the cortical partes of lenses were prepared and immersed into a fixative solution containing 2% paraformaldehyde and 2.5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) for more than 4 hours at room temperature or overnight at 4 degrees C. The specimens were then postfixed, dehydrated and embedded in a mixture of Epon 812 and Araldite. Ultrathin sections stained with uranyl acetate and lead citrate were evaluated by electron microscopy (Philips-300). Microscopical examination of the cortical layer cells of lenses showed extensive cellular vacuolization, calcification, and formation of a light scattering center. Cortical fibers were found to be compacted along their length, and elongated with decreased interdigitations.