We have developed an office-based dot-EIA for the detection of a urinary high molecular weight cytokeratin (CK). Immunohistochemical staining and western blot based on CK1K10 monoclonal antibody were used to identify the CK. Urine of 192 patients with different types, grades, and stages of bladder tumor and 72 controls were evaluated using dot-EIA. An intense and diffuse cytoplasmic reaction was shown in bladder squamous cell carcinoma. The target epitope was identified in urine at 65, 56, and 40-kDa. The CK purified from urine showed single polypeptide at 65-kDa using SDS-PAGE and single peak at 7.4 min using capillary zone electrophoresis. The dot-EIA detected the CK with high sensitivity (97%) and specificity (94%). The CK was not detected in urine of bladder cancer patients showing response to radiotherapy. The sensitive and specific office-based detection of urinary cytokeratin would be helpful in rapid diagnosis and follow up of bladder carcinoma.