Abstract Context.—Fluorescence in situ hybridization (FISH) of voided urine sediment is a sensitive and specific test for the detection of urothelial carcinoma. The time required for slide preparation using the conventional cytospin method is lengthy. Objective.—To present an alternative to the conventional cytospin method. Design.—We compared the results of an improved filter monolayer method with published results of the conventional cytospin method. A total of 624 patients with cytology and FISH analyses were followed with cystoscopy and/ or bladder biopsy. Fluorescence in situ hybridization analysis was performed on 624 cases using fluorescence-labeled probes to the pericentromeric regions of chromosomes 3, 7, and 17 and band 9p21; cytology was also performed in all cases. Results.—A total of 217 (34.7%) of 624 patients had follow-up bladder biopsies, and 170 of these (78.3%) had urothelial carcinoma. The sensitivity for cancer detection was higher for FISH than for urine cytology (92.9% [158/ 170] fo...