This study was carried out in order to examine the influences of grinding wheel hardness on surface roughness and grinding forces during surface grinding. Grinding tests were carried out using Al(2)O(3) grinding wheels with I, M and Q hardness grades at different table speeds and at different depth of cuts. AISI 1050 (50 HRc) and AISI 4140 steels (52 HRc) were used as the workpiece materials. In order to measure the grinding forces generated during grinding, the dynamometer previously designed and manufactured was used. This dynamometer was also connected to a personal computer to save the grinding force data. The roughness of surfaces were also measured. It is seen significant increases on surface roughness by increasing wheel hardness and grinding forces. The grinding operations carried out using grade I grinding wheels produced higher surface roughness and mean grinding force values by 53.5% and 59.8%, respectively, than those obtained by grade Q grinding wheel.