Abstract: Adhesion to cells and matrices participates in the regulation of lymphocyte proliferation, maturation and tissue localization. Consequently, abnormal patterns of adhesion molecule expression may contribute to the pathophysiology of lymphoprohferative disorders. Integrins are major cell‐surface adhesive proteins composed by a and β subunits. In contrast to normal lymphocytes, Burkitt's lymphoma (BL) cells lack the β2 integrin CD11a/CD18. To study the molecular mechanism underlying this deficiency, presence of the transcript for each subunit was analysed by Northern blotting in group I BL lines (BL biopsy‐like) and, for comparison, Epstein‐Barr virus (EBV)‐transformed lymphoblastoid cell lines (LCLs). While transcripts for both CD11a (α subunit) and CD18 (β subunit) were readily detected in LCLs, BL lines contained the transcript for the α subunit only. Treatment of BL cells with phorbol ester for 72 h induced expression of the β subunit mRNA and the CD11a and CD18 antigens on the cell surface. The results indicate that the CD11a/CD18 deficiency of BL is due to absence of the β subunit transcript and that this defect is restored by stimulation of the cells.