Type D retroviruses cause immunodeficiency in monkey. Earlier we have revealed genetical and serological markers of type D retroviruses in children with Burkitt-type lymphoma. Using PCR/Southern blotting assay we have found sequences related to MPMV in PBMC's DNA from children with Burkitt-type lymphoma and from their parents. Moreover, the data on sequencing of virus specific sequences from one ill child and from his mother have been presented. © 2001 Elsevier Science B.V. All rights reserved.