Myocardial fibrosis is a frequently observed pathologic finding. It is a common practice to differentiate macroscopic scarring and microscopic scarring, but there has been little attempt to distinguish the various types of interstitial fibrosis, and to determine their prevalence in different cardiac disorders. In this study, we have semiquantitatively assessed microscopic scarring, interfibre and perivascular fibrosis and a distinctive type of plexiform fibrosis. We examined ten hearts with congestive cardiomyopathy, ten with hypertrophic cardiomyopathy, ten with severe valvular aortic stenosis and ten normal hearts. Perivascular and interfibre fibrosis were quantitatively closely linked and most marked in the congestive cardiomyopathy and the valvular aortic stenosis groups. Plexiform fibrosis occurred maximally in the hypertrophic obstructive cardiomyopathy group, closely associated with myocardium exhibiting muscle fibre disarray. Our study demonstrates that although different types of interstitial fibrosis have particular associations with certain disease entities, the associations are not specific. The recognition of the prevalence of one or more types of interstitial fibrosis may, however, assist in the histopathologic diagnosis of certain myocardial disorders.