In the course of routine pretransplant cadaveric donor kidney biopsy examination, specimens from two donors were found to exhibit intense mesangial localization of IgA by immunofluorescence, with the presence of large immune complex-type deposits in these areas confirmed ultrastructurally. Both kidneys from each donor were transplanted with the ultimate result that three of the four kidneys underwent early irreversible rejection and were removed within 3 months, while the fourth kidney has maintained normal function for a period of 8 months. Morphological and immunofluorescent evaluation of the rejected kidneys at the time of nephrectomy showed minimal residual IgA mesangial deposits, but all had changes indicative of severe acute allograft rejection. These findings suggest that glomerular lesions involving mesangial IgA deposition can resolve fairly quickly following transplantation, but that the risk of irreversible acute rejection might be greater in the recipients of such kidneys.