The anisotropic thermal expansion of the hexagonal elements, thallium, yttrium, beryllium, and zinc, has been measured. The temperature range for the thallium, yttrium, and zinc measurements was 4.2−273.2°K, while for beryllium the range was 77−273.2°K. Dimensional changes were detected by an interferometric technique, and the movement of the interference fringes was detected with a photomultiplier tube. From the measured values of &Dgr;L/L0the coefficients of thermal expansion and thec/aratios of the metals were calculated as a function of temperature. A review of previous measurements of the thermal expansion of these metals is also included.