Serum levels of sICAM-1 and sVCAM-1 adhesion molecules as well as TNF cytokine were measured in 50 kidney transplant recipients [14 patients with stable graft function, 18 patients with acute rejection, 10 patients with CsA toxicity, 6 patients with ATN, and 2 patients with cytomegalovirus (CMV) disease] during the first 3 postoperative weeks. All the patients studied showed, on the first posttransplant day, elevated serum levels of sICAM-1 (260 +/- 53 ng/mL). Interestingly, all the patients with good graft function presented thereafter a reduction of sICAM-1 serum levels close to the normal values (185.2 +/- 40 ng/mL). In contrast, the group of patients with acute allograft rejection showed significantly increased serum levels of sICAM-1 (371.5 +/- 86 ng/mL; p < 0.001), 3-4 days before diagnosis of acute rejection. Although sVCAM-1 levels were increased in both acute graft rejection (2263 +/- 106) and CsA toxicity (1650 +/- 315) patients, such increase was not significant among either group of patients when the group with CsA toxicity was compared with either ATN (1320 +/- 204) or stable renal function (1089 +/- 167). No statistical differences in the levels of TNF were demonstrated between the different groups of patients studied. Our findings demonstrate that quantitative determination of serum sICAM-1 may be of predictive clinical value in transplanted patients with acute renal allograft rejection.