Since the first description of cytomegaly as "disease with protozoan-like cells" more than 50 years have past until a definitive explanation of the viral aetiology was reached. In the eighties cytomegaly gained increasing importance in adults. This event was based upon the occurrence of cytomegaly especially in patients with organ transplantation, AIDS infection, chronic dialysis or chemotherapy of malignant tumours. With the development of immunohistochemistry (IHC), in situ hybridization (IHS) and polymerase chain reaction (PCR) new, more sensitive methods became available to detect CMV infections especially in biopsy specimens or cytological material. With IHC, ISH and PCR CMV verification is possible in seemingly normal cells without inclusion bodies. PCR can be used also on small biopsy particles of paraffin-embedded material and is characterized by high specificity and sensitivity. The parallel performance of IHC and ISH was proved to be useful in routine diagnostic work, whereas PCR should be used especially in diagnostically different cases. The methods of the evidence of CMV infection are analysed in the different organs.