Systematic research of the biopsy and autopsy tissue specimens of patients with systemic lupus erythematosus (SLE) characterized all aspects of immune deposits and confirmed their key role in the pathogenesis.It additionally drew attention to the involvement of other immune factors, particularly antiphospholipid antibodies, as well as nonimmune mechanisms.Our study of ANCA positive vasculitis in the kidney revealed histopathologic differences associated with the ANCA specificity for myeloperoxidase and proteinase 3 despite their likely common pathogenesis. Our study of Balkan endemic nephropathy pointed out the role of the chronic changes of the intrarenal vasculature in the pathogenesis. Demonstration of the the aristolochic acid DNA adducts in the tissue samples contributed to the understanding of the etiopathogenesis of this disease, which could be the result of a long-term exposure to low concentration of phytotoxins and mycotoxins in the endemic environments. Our research results were published in the international monograph on tubulo-interstitial and vascular renal diseases, representing the basic guidance for the classification and diagnosis of these diseases, prepared under the auspices of the World Health Organization. The results of our study of monoclonal immunoglobulin deposition diseases contributed to their classification and understanding of their pathogenesis. The study of thrombotic microangiopathy associated with cyclosporine therapy in patients with kidney transplant pointed out differences in intensity of the glomerular and extraglomerular vascular changes and drew particular attention to the frequently limited focal involvement with a favourable prognosis. In our study of the hemorrhagic fever with renal syndrome it was confirmed that the endothelial cells of the small blood vessels, particularly in the outer medulla, are the main target of hantaviruses. Histopathologic picture in hantavirus infection was found to be represented by severe congestion, acute injury of the endothelial cells, disruption of small blood vessels and hemorrhages. It appears that these changes are predominantely the result of the harmful effect of various cytokines released from the infected cells. Our research contributed significantly to better understanding of cancerogenesis of the head and neck carcinoma (reactivation of the telomerase, alterations in cell cycle gene and protein expression, stromal reaction) and improved our knowledge of diagnostic and prognostic factors, thus enabling to choose more appropriate treatment of precancerosis and squamous carcinoma of the head and neck. The Ljubljana classification of the precancerous lesions of the larynx is now internationally recognized. Members of our research team have been invited to write several chapters for the new WHO book "Pathology and Genetics of the Head and Neck Tumours": on precancerous lesions of the larynx and hypopharynx, on laryngeal papillomas, on squamous carcinoma of the larynx and hypopharynx, and on its subtypes. The results of our research have been presented as invited lectures on three European Congresses of Pathology and two Intercontinental Congresses of Pathology as well as on several other international and domestic scientific meetings. Molecular genetic investigations included studies of cancer, some common hereditary diseases and development and optimization of methodologies for detection of variations in disease genes. We showed that determination of microsatellite instability (MSI) in combination with the methylation status of MLH1 promoter represented a powerful way for identification of families with hereditary non-polyposis colorectal cancer. We found out that suppressor pathway connected with low MSI and high loss of heterozygosity was dominant in the cancerogenesis of squamous cell carcinoma of head and neck.