The Danish Renal Biopsy Register, created in 1985, is a comprehensive national register of all renal biopsies performed in Denmark. It includes light microscopy diagnoses, immunofluorescence information, disease localization, and clinical information. The number of registered biopsies has remained constant since inception at 570/year, 200 of which are from renal allografts. Biopsy analysis is performed in five regional specialist renal pathology departments, resulting in a high degree of compliance. Diagnosis intercenter reproducibility has been analyzed. The existence of a unique personal identity number permits easy linkage to other national databases, including the national population register, the dialysis and transplantation register, and the cancer register. Studies concerning the relationship of glomerulonephritis to cancer incidence, and the incidence and prognosis of glomerulonephritis and diabetic glomerulopathy have been published. The database is available for international studies on approval by the executive chairman.