1. Data obtained since the implementation of the T-cell flow cytometry crossmatch (T-FCXM) on a prospective basis verify the effectiveness of the T-FCXM for sensitized patient groups. Relative ineffectiveness of the T-FCXM when applied to nonsensitized patient groups is due to substantially reduced sensitivity for these patient groups. 2. Overall, a T-FCXM reaction of greater than 10 channels is associated with increased incidence of kidney nonfunction at 1-month posttransplant. Higher antibody levels, indicated by T-FCXM reactions of greater than 20 channels, are associated with increased incidence of kidney function delayed beyond the first week posttransplant. 3. The platelet FCXM (PL-FCXM) is somewhat more specific, but also somewhat less sensitive than the T-FCXM. Generally speaking, raising the threshold for defining a positive T-FCXM from the standard 10 channels to 20 channels results in performance similar to that of the PL-FCXM, when the tests are used individually. 4. The PL-FCXM used in conjunction with the standard T-FCXM can substantially reduce the false-positive rate of the T-FCXM, thus increasing the usefulness of the FCXM significantly. 5. We hope that the T-FCXM has contributed to continued improvement in renal transplant outcome over the past few years. However, from the number of cases of sensitized patients being transplanted across a positive FCXM, it appears that many more cases of nonfunctioning transplanted kidneys could be avoided by fully implementing the T-FCXM for sensitized patients.(ABSTRACT TRUNCATED AT 250 WORDS)