The acute and insidious onset of pulmonary metastatic transitional cell carcinoma. Transitional cell carcinoma is a common urologic neoplasm. Although pulmonary metastases from this tumor are often not appreciated clinically, they are frequently documented in autopsy studies. Therefore, the clinical recognition of this condition can be problematic. To illustrate this point, we present three patients with progressive unexplained dyspnea and histories of transitional cell carcinoma. Since ineffective and possibly detrimental therapeutic approaches may be initiated, a high index of suspicion for pulmonary metastatic embolization must be maintained. Early histologic identification of these metastatic emboli and initiation of effective chemotherapy may prove beneficial for improved quality of life. 