The value of the so-called lupus erythematosus (L. E.) inclusion phenomenon of bone marrow and blood as an aid in the diagnosis of acute disseminated lupus erythematosus has been amply demonstrated.1It is the purpose of this paper to report a case of pericardial effusion due to acute disseminated lupus erythematosus in which the diagnosis was first intimated by the finding of L. E. cells in the Wright-stained buffy coat smears of the patient's oxalated pericardial fluid. Subsequently, large numbers of L. E. cells were demonstrated in buffy coat preparations made from an oxalated marrow specimen from the same patient. Response to cortisone therapy was striking and led to rapid resorption of the pericardial effusion. REPORT OF A CASE A 38-year-old white woman was well until May, 1950, at which time pain developed in the right thigh, with subsequent pain and swelling in the right leg and foot. In