We present the clinical findings in the thirteenth recorded patient with lymphedema, pleural effusions, and ungual dystrophy--the so-called "yellow nail" syndrome. The rate of pleural-fluid turnover was measured by using radioiodinated albumin to trace the efflux of fluid by lymphatics. The rate of pleural lymphatic flow was low in comparison to previous estimates obtained by the same method in a variety of other conditions. Such slow lymphatic flow is consistent with the postulate that accumulation of pleural fluid in this syndrome is due to defective lymphatic drainage.