In the REAL classification, diffuse large B-cell non-Hodgkin's lymphomas are grouped together. We investigated histological variants and immunohistochemical profile of diffuse large B-cell lymphomas in 53 patients. Accuracy of the diagnosis was 73.6% without immunohistochemistry. The usefulness of immunophenotyping in making the correct diagnosis depended on a specific histological variant of diffuse large B-cell lymphoma. Variants with polymorphic and anaplastic morphology or massive reactive component have been diagnosed by routine histological methods with poor validity.