In this study, an attempt to investigate the role of isothermal aging on the microstructure and dry sliding wear behavior of Co-28Cr-5Mo-0.3C alloy was made. Regarding the results, it is clear that isothermal aging at 850 A degrees C for 8 and 16 h contributed to the formation of lamellar type carbides (gamma-fcc + M23C6) at the grain boundary regions. Moreover, at higher aging times (24 h), the lamellar type carbides decreased whereas severe precipitation of carbides was found to occur on the stacking faults. Furthermore, according to X-ray diffraction results, 24 h isothermal aging of solution treated specimens did not lead to complete fcc -> hcp transformation. The wear properties of as-cast and heat treated samples were determined at 0.5 ms(-1) speed several under normal applied loads such as 50, 80, and 110 N. At the lowest load applied (50 N), isothermally aged specimens for 8 and 16 h have higher wear resistance probably due to more volume fraction of lamellar-type carbides when compared to as-cast for both 4 and 24 h aged specimens. But, at higher applied loads (80 and 110 N) due to the formation of adhesive oxide layer on the as-cast specimen surface, the wear rate of as-cast samples is lower compared with all heat treated specimens.