Leukocyte adhesion deficiency (LAD) was suspected in a three weeks old girl from a family with an established history of LAD with a lack (less then 1%) of the beta 2 integrins CD 11a, b/CD 18 expression at the leukocytes surface, was engrafted with her mother HLA identical bone marrow at the age of 14 months. Repeated post transplantation (up to 22 months). Immunological assessments showed a good engraftment with 97% of the lymphocytes expressing CD11a/CD18. Cells proliferated normally in response to PHA and to Tetanus toxoïd after revaccination. The level of serum immunoglobulins was normal. Investigation of the CD18 intragenic polymorphic marker Avall before and after bone marrow transplantation (BMT) showed a transition from the Avall +/+ genotype to the mother's Avall +/- genotype. Similarly DNA fingerprints obtained with the patient genomic DNA, prepared from PBMC, prior and after transplantation, showed that the patient's DNA fingerprints pattern matched the mother's one. These findings are consistent with the good engraftment observed clinically. This study emphasizes the usefulness of the molecular techniques to evaluate the degree of chimerism in monitoring the outcome of bon marrow transplantation.