To evaluate the usefulness of performing pleural biopsy in every patient with undiagnosed pleural disease, regardless of the presence of fluid, a total of 222 biopsies were performed in 163 patients with use of the Abrams needle technique. In the last 48 specimens, culture in 7H-9 liquid medium was routinely performed. In all biopsy specimens, pleural disease was found. In 61 instances, a specific histological diagnosis of either neoplasia or tuberculosis was made. In 80% of the biopsy specimens with histological evidence for tuberculosis, the cultures of the specimens were positive. Thirty-five biopsies were done in the absence of pleural fluid and were as diagnostically successful as those done in the presence of fluid. Pleural biopsy is indicated in any case of undiagnosed pleural disease, even if free fluid is not present.