The diagnostic yield of bladder wash cytology was compared with concurrent bladder biopsy results in 253 consecutive cytology specimens obtained from 208 patients. There was high diagnostic concordance of washes and biopsies for both high grade urothelial neoplasms (26 of 29 cases [90.0%]) and negative specimens (152 of 168 cases [90.5%]). In contrast, bladder wash cytology was interpreted as malignant or suspicious for malignancy in 11 of 33 (33%) patients with low-intermediate grade papillary urothelial tumors on biopsy. Additionally, the cytology was considered positive or suspicious for transitional cell carcinoma in 11 cases in which only reactive changes were seen in the concurrent biopsy and follow-up studies (minimum 12-month follow-up), for a false-positive rate of 6.5%. The slides from all discrepant cases were reviewed, with particular attention to background features that may improve the diagnostic sensitivity of cytology in low grade neoplasms.