Data on the elastic properties of corneal tissue are needed to define the parameters involved in a model for radial keratotomy. Using bovine corneal tissue, we measured stress-strain relationships of tissue at different locations in the cornea. From this data we calculated Young's modulus of elasticity of five specimens at peripheral and central corneal locations. Increasing levels of stress produced increased resistance to stretch, a property typical of soft biologic materials such as cornea. Linear regression analysis of the data showed that the elastic modulus of the peripheral tissue was greater than that of central tissue at all values of applied stress. These linear relationships were statistically different, using an analysis of covariance, indicating that peripheral corneal tissue is stiffer than central corneal tissue. This information supports the suggestion that a peripheral circular ligament of corneal tissue exists and helps to maintain the curvature of the cornea. It is the disruption of this ligament that is believed to cause some of the change in corneal curvature when radial keratotomy is done.