1. Physiological salt solution is absorbed from the pericardial cavity of medium-sized rabbits at a rate of approximately 1.3 cc. per hour. This absorption is via the subepicardial blood capillaries. 2. Rabbit serum and horse serum are absorbed extremely slowly-an indication of the low-grade lymphatic drainage of the pericardial sac. 3. Graphite particles of bacterial dimensions are also removed very slowly. Such particles enter lymphatics only after phagocytosis. The lymphatics in the basal part of the pericardium are the principal source of drainage. Subepicardial lymphatics are entered with difficulty from the pericardial cavity.