Clinical usefulness of a newly developed assay kit for ACB (SD-8828) which detects urinary bacteria coating IgG was evaluated and compared to the enzyme antibody plate method. A total of 48 patients including 20 patients with acute simple cystitis and 28 patients with acute or chronic pyelonephritis, who were shown to have pyuria of at least 5 cells/HPF, bacteriuria of at least 10(4) CFU/ml were enrolled in this study. By enzyme antibody method. ABC was positive in 92.9% of patients with upper urinary tract infection and negative in 100% of patients with lower UTI, this difference being statistically significant (p < 0.02). By SD-8828, 85% of positive coincidence rate and 100% of negative coincidence rate, compared to the enzyme antibody technique, was obtained. The overall coincidence rate was high (91.7%). This SD-8828, a new simple assay for ACB, which detects IgG alternating the plate method, may be used as a convenient method in clinical practice.