Abstract: A method and apparatus for measuring the linear thermal expansion of a polymeric material wherein a sample with a wedge surface is mounted on a graphite block within a temperature controlled chamber. The incident and reflected beam of a laser lie in a plane perpendicular to the plane of the base of the sample and make equal angles with a line perpendicular to the plane of the base of the sample. A holographic plate is exposed by the object beam from the sample and a reference beam. The temperature is gradually increased from 0.9.degree. to 4.degree. F. between a first exposure and a second exposure. A thermocouple and indicator are used to indicate the temperature of the sample at the time of each exposure of the holographic plate. The holographic plate is then developed and replaced in the plate holder for reconstruction of the images and the fringe pattern, which indicates the expansion of the sample.