Despite overall improved graft survival, renal graft thrombosis (RGT) remains an important cause of graft loss. Of 6153 consecutive renal transplants (RTx), 134 index cases of graft loss from RGT were reported to the Australian and New Zealand Dialysis and Transplant Registry between 1980 and 1992. Two groups were selected for comparison: (1) institutional controls (n=127), the previous RTx at the same institution as each index case; and (2) graft controls (n=107), the contralateral cadaveric donor kidney of each index case. RGT cases that coincidentally occurred in control groups were deleted from those groups (6 of institutional controls, 2 of graft controls). RGT within the first 30 days after RTx occurred in 1.9% of all RTx and was constant from 1980 to 1992. In contrast, RGT caused an increasing proportion of early (within 30 days of RTx) graft losses (P=0.01). The cumulative occurrence of RGT in those who thrombose was 62.6%, 83.7%, 90.2%, and 93.5% at 2, 7, 14, and 30 days after RTx, respectively. By comparison, with the control groups, no association with RGT was demonstrated for recipient age or sex, primary renal disease, type of dialysis, treatment with CsA, degree of HLA mismatch, panel reactive antibody levels, perfusion solution and perfusion technique, or immunosuppressive therapy. There was a significantly increased incidence of RGT with both extremes of donor age, female donors, and prolonged total ischemic time.