Measurements made at the National Standards Laboratory and at Iowa State University of the linear expansion coefficient a for Si, Cu, Ag, Al and Ge below 35 K agree within limits of experimental uncertainty and should constitute reliable reference data. At temperatures from 35 K toca100 K, there are data for Cu measured at NBS and by Rubinet al.which disagree by ∼10 7times; 10−8K−1. From 130 to 230 K these and Russian data agree well but above 230 K they differ, the difference reaching 10 × 10−8K−1 near room temperature. Comparison of &agr;‐values for Si is a useful guide when considering the reliability of these reference data.