PROBLEM:Lymphocyte immunotherapy (LIT) is applied in infertility treatment. Moreover, it has been suggested for prevention of rhesus D-hemolytic disease and as a vaccine for reduction of human immunodeficiency virus-1 susceptibility. Although transfusion-related problems have been rarely reported they were a matter of debate. Here we discuss extensive single-center experience with intradermal LIT for implantation failure and recurrent miscarriages. METHOD OF STUDY:Retrospective 2- to 3-year follow-up of in vitro fertilization couples treated during 1996-2002 (feedback 2,848/3,041 = 93%), registering 930 deliveries. Prospective survey for acute reactions for 2000-2003 (feedback 2,687/3,246 = 83%). Review of the literature. RESULTS:Infections of the patient and transplant rejection later in life are minor residual risks. Post-transfusion purpura was suspected once but not verified. Anaphylaxis or malignancy were not promoted. Fetal/newborn alloimmune disease (severe hemolytic disease, thrombocytopenia, neutropenia) were not observed. CONCLUSION:Based on microbiological, immunological, and hematological testing the risks of intradermal LIT are low.