The influence of blood transfusions, HLA, A and B, DR matching was studied in adult patients transplanted in one centre. The conclusions were: 1. Pre-transplant blood transfusion(s) are a prerequisite for graft acceptance. 2. In transfused patients with no HLA A and B mismatch, there is only 8% graft loss due to irreversible rejection. 3. In transfused patients with a functioning graft after six months, a decrease in the number of reversible rejection crises is observed in patients with no HLA A and B mismatch or with identity for HLA B7 or HLA B8. 4. Identity for HLA B7 or B8 also gives a higher chance of a late onset of the first rejection crisis.