In this experimental study, the strip-formed specimens made from aluminum alloy 1030, pure Cu, CuSn7, CuZn30, and low-carbon steel 6114 were cold worked to different ratios. To determine the microhardness values of the materials, microhardness tests were applied. The grain sizes of the materials were determined by the Heyn method, using a metal microscope. The hardness of materials, H, is dependent on the grain diameter, d, in a way similar to the yield stress in the Hall-Fetch relation H = H-0 + K(H)d(-1/2), where H-0 and K-H are constants. The microhardness of the materials was found, with reasonable accuracy, to vary with grain size according to the Hall-Fetch equation. (C) 2000 Elsevier Science Ltd.