A fused quartz differential dilatometer was interfaced with a mini‐computer to automatically measure the thermal expansion of solids from 300 to 1000 K. An electronic micrometer, readable to2.5 × 10−6 cm, was employed for length change measurements accurate to2.5 × 10−5 cm. Calibrated thermocouples were used to measure temperature changes to±0.27 K. The complete experimental procedure was under computer control and involved : (a) Regulating the power to the furnace to achieve thermal equilibrium (2–5 hr); (b) Measuring the specimen temperature and length change (1 min.); (c) Remeasuring the specimen temperature and length change to check thermal equilibrium of specimen (15 min.); (d) Increasing or decreasing the specimen temperature to the next set point (1 hr).The software and hardware necessary to accomplish the measurements are described. Measurements on National Bureau of Standard certified fused silica, copper, and tungsten are presented and demonstrate an uncertainty of about±1 × 10−7 K−1in the determination of the coefficient of thermal expansion. The influence of metallurgical creep above 600 K on measurements on copper are discussed and results on commercially pure copper are presented.