Lymphangiography is proving to be an important diagnostic method in determining the anatomic integrity of the lymphatic network. This procedure permits direct visualization of nodes and lymph channels in areas of the body remote from the clinician's palpating fingers (5). It is particularly useful in studying the pelvic and retroperitoneal nodes which, short of surgery, were previously accessible to investigation by indirect methods only (15). Present evidence suggests that lymphangiography may enable the differentiation of metastatic deposits produced by carcinoma from those produced by lymphoma (2, 14, 21, 25). Furthermore, the precise site and extent of tumor spread may be demonstrated. Such information is essential to the therapist in evaluating the stage of disease, as well as in deciding upon the optimal mode of treatment. Although a number of reviews of the role of lymphangiography in diagnostic medicine have appeared (21, 25), there has been scant discussion of the complications following the use of oily contrast media in the lymphatic system. This paper will explore one major complication, namely, pulmonary Ethiodol embolism, with respect to its incidence, manifestations, and pathogenesis. Method and Material The technic of lymphangiography employed in this institution (Stanford University School of Medicine) is essentially similar to that outlined by Kinmonth (10–12) and modified by Wallace et al. (25). Following the injection of 0.5 to 0.7 c.c. of equal parts of Evans blue and 1 per cent procaine into the web space between the first and second toes, the lymphatics may be seen stained on the dorsum of the foot. A half hour later, linear cut-downs are performed on the dorsum below the ankle, and a lymphatic channel is isolated and cannulated with a 30-gauge needle connected to No. 160 polyethylene tubing. Warmed Ethiodol (an iodized poppy-seed oil) is employed as a contrast agent and is delivered into the lymphatic channel by means of an automatic constant-speed injector, at a rate of 12 c.c. per hour. No more than 20 C.c. is injected when both lower extremities are cannulated, and a maximum of 10 c.c. is employed in a single injection into one lower extremity. Immediately preceding and following introduction of the medium, films of the chest, abdomen, pelvis, and lower extremity are obtained. These roentgenographic studies are repeated at twenty-four and/or forty-eight hours. Throughout the procedure, the patient rests comfortably on a foam-rubber mattress on the surface of an x-ray table. Fluoroscopic and roentgenographic monitoring of the injection is an essential part of the examination. Lymphangiography has been performed successfully on 80 patients for the purpose of evaluating the presence and degree of neoplastic involvement of the pelvic and abdominal retroperitoneal nodes. All patients had a biopsy-proved diagnosis of malignant disease.