SUMMARY The Barbeito-Lopez trichrome stain (BLTS) was compared with hematoxylin and eosin (HE), the basic fuchsin picric acid (BFP) and nitro-blue tetrazolium (NBT) dye tests. Two types of hearts were studied: a) myocardial necrosis induced by isoproterenol (ISP) in rats and b) human hearts with early coagulation necrosis (Early CN). The BLTS was much more sensitive than HE for diagnosis of Early CN in rats. By 24 hours, both BLTS and HE showed established coagulation necrosis (Established CN) although BLTS did so more clearly. In human material BLTS was a useful indicator of Early CN. It showed patchy areas of coagulation necrosis in the cytoplasm of damaged myocardial cells which were not visualized with HE. Normal myocardium remained green or pale blue. Early CN appears as patchy yellow areas while the remainder of the cytoplasm stains green. Established CN appears" golden yellow" or" orange yellow".