Abstract: A method and apparatus for determining crack growth in an elastomer. A horizontally elongate elastomeric test specimen is cyclically stretched crosswise by upper and lower rigid plates contiguously attached to the long edges on both sides. The lengthwise growth of a crack induced by a small cut at one vertical edge of the specimen is determined by measuring the stretching force at each end. The lower plate is reciprocated by a hydraulic actuator relative to the upper plate. Two load cells measure the forces at each end of the specimen. With the use of a computer program and the relative forces measured by the load cells, the crack growth can be calculated.