The presence of anti-tissue antibodies in sera from patients with genitourinary carcinomas and non-malignant genitourinary diseases was studied by indirect immunofluorescence. An increased incidence of various tissue antibodies was observed in carcinomas of the urinary bladder, prostate and kidney when compared to controls. There was a trend towards association between antinuclear antibodies and metastatic undifferentiated tumors. A low degree of malignancy was associated with antibodies against connective tissue "reticulin". A striking similarity between tissue antibody "patterns" in carcinoma patients and patients with chronic renal inflammation was seen. This points to inflammation as being an important factor in tissue antibody production.