A high-precision Fizeau type, laser interferometric dilatometer has been developed and used to measure the thermal expansion of metal matrix composites. The strain resolution of this dilatometer system is about 1 × 10⁻⁶. The thermal expansion of graphite/magnesium and graphite/aluminum composite laminates were measured over the temperature range of 117 to 394 K. The expansion of a P100 graphite/6061 aluminum (P100 Gr/6061 Al) unidirectional laminate was measured and compared with an approximate nonlinear analysis. The good agreement obtained between analytical and experimental results was further improved when temperature dependent properties were included in the analysis. Data showed that the behavior of the specimen at the end of the first thermal cycle was path dependent during the cycle. Test data on a P100 Gr/AZ91C Mg undirectional laminate indicated a lower coefficient of thermal expansion and smaller residual strain than P100 Gr/6061 Al after thermal cycling between about 117 and 394 K.