Films of photosensitive polyurethanes based on castor oil and bearing increasing amounts of cinnamoyl groups were obtained and submitted to tensile tests and thermogravimetric analysis. The test samples were cut into strips, with the long axis making angles of 0, 30, 45, 60, 90, 120, 135, and 150 degrees with the suspected direction of anisotropy. In another series of experiments, films were irradiated with a high pressure mercury lamp during different periods of time and again submitted to tensile tests.