The sensitivity of voided urinary cytology (VUC), bladder wash cytology (BWC), and bladder wash flow cytometry (BWFCM) in detecting cancer was studied in 70 patients with biopsy‐proven bladder tumors. There were 11 Grade I papillomas, 14 Grade II TA, 18 Grade II‐III TIS, 19 Grade II‐III T1, and eight Grade II‐III T2 carcinomas. One to five VUCs per patient (mean, 2.63) were obtained within the 24 hours preceding biopsy. At endoscopy a bladder wash specimen was obtained and divided for cytologic and flow cytometric examinations. For all tumor categories combined, the sensitivity for one, two, and three voided cytology examinations per patient was 41%, 41%, and 60%, respectively. The sensitivity of a single BWC was 61%, of a single BWFCM, 83%. Thus, one BWFCM is more sensitive than three VUC (binomial test; P = 0.006); one BWC is more sensitive than two VUC (P = 0.01); and one BWFCM is more sensitive than one BWC (P = 0.003). These findings remain significant when papillomas are excluded from the analysis (P ≤ 0.03) and when papillomas and T2 tumors are jointly excluded (P ≤ 0.02). Only four of 70 patients (6%) had their cancers detected by VUC and/or BWC rather than BWFCM. In summary, irrigation cytology specimens are more sensitive than voided urinary cytology, and bladder wash flow cytometry is more sensitive than either in diagnosing bladder cancer. Flow cytometry is more sensitive because of the better sampling of bladder irrigation compared with voided urine and because of the measurement technique itself.