A 65-year-old female presented with a one-and-a-half-year history of intermittent, painless, gross hematuria. She was found to have a large bladder neoplasm. A cytologic diagnosis of signet-ring-cell (colloid) carcinoma was made on a bladder washing and was confirmed histologically by a cystoscopic biopsy. Subsequently, a radical cystectomy was performed. The cytologic findings of this rare pure signet-ring-cell carcinoma of the bladder, not previously described, are presented along with the histologic and ultrastructural findings.