In the present study the possibility of immunophenotyping of routinely prepared (air dried) peripheral blood and bone marrow smears is described after storage. The immunoenzymatical alkaline-phosphatase-anti-alkaline-phosphatase (APAAP)-method was carried out in differently stored blood smears (+4 degrees C and -80 degrees C). Last results were compared with originals made from freshly prepared mononuclear cells at time of diagnosis. The results showed no remarkable decrease of antigenicity, neither under the procedure refrigeration and thawing of the frozen smears (-80 degrees C), nor under storage conditions of more than 22 months. In our opinion this highly sensitive method enables us to get additional results from unexplained haematological disorders using retrospective analysis.