BACKGROUND Progress in non-invasive diagnostic techniques such as ultrasonography, computerised tomography or magnetic resonance caused a significant decrease in the use of diagnostic myocardial biopsy (DMB). However, recent advances in molecular biology and widening knowledge about the role of new biochemical markers gives hope for more detailed assessment of cardiomyocyte pathophysiology, based on the proper examination of myocardial biopsy specimen. AIM To assess current usefulness of DMB in the diagnosis of various myocardial disorders and monitoring after heart transplantation. METHODS DMB was performed in 104 patients (84.6% males) with a clinical diagnosis of idiopathicdilated cardiomyopathy (35.6%), post-inflammatory dilated cardiomyopathy (22.1%), restrictive cardiomyopathy (2.9%), post-infarction myocardial injury (17.3%), ventricular arrhythmias resistant to treatment (2.9%), cardiac tumour (0.96%), suspected arrhythmogenic right ventricular dysplasia (0.96%) and with transplanted heart (17.3%). In each patient 3-4 specimens of the right ventricular cardiac muscle were taken. Immunohistochemical reactions were used to assess the presence of desmin. Myocarditis was diagnosed on the basis of morphological assessment of specimens stained with HE, Mallory trichome and immunohistochemical methods which identified lymphocytes T (CD3, OPD 4, UCHL1), endothelium (CD34) and antigen MHC II (DP, QR). In addition, specimens suggesting laminopathy or amyloidosis were examined under electron microscope. RESULTS DMB revealed the absence of desmin (19.2%), abnormal concentration of desmin (21.1%), myocarditis (19.2%), so-called vascular myocardial injury (16.3%), other proteinopathies (2.3%), amyloidosis (1.9%), connective tissue diseases (0.96%), arrhythmogenic right ventricular dysplasia (0.96%), toxic injury (0.96%) and normal myocytes (0.96%). CONCLUSIONS Our results suggest that complex analysis of myocardial biopsy specimen provides detailed information of the pathogenesis of cardiac disorders. However, further progress in molecular biology is needed to achieve more complete diagnosis.