Four cases of disseminated adenocarcinoma of the prostate illustrating the clinical spectrum of intrathoracic involvement in this disease are presented. In two cases the presenting features of prostatic cancer were with lymphangitis carcinomatosa and an isolated pleural effusion, whereas two other cases developed intrathoracic metastases in the setting of previously known locally advanced prostatic cancer. In one this took the form of hilar and mediastinal lymphadenopathy and in the other that of pulmonary nodules. An immuno-cytochemical marker for prostatic specific antigen, a highly sensitive and specific tool for identifying prostatic epithelium, identified the prostate as the primary site of malignancy in the first two cases. Symptomatic and radiological responses were noted in all four cases after bilateral orchidectomy. Pulmonary metastases are common in the advanced stages of prostatic cancer but may also be present at the initial presentation with the disease even when the primary tumour is not clinically apparent. We recommend that (i) immuno-cytochemical stains for prostatic specific antigen are applied to all lung, pleural and mediastinal biopsy specimens showing adenocarcinoma in male patients, and (ii) all males with intrathoraic adenocarcinoma have prostatic aspiration cytology performed if the prostatic specific antigen stain is positive.