Objective: The purpose of the present study was to determine the variations in the drainage patterns of middle lobe vein of the right lung. Methods: Right lungs of 30 formalin fixed cadavers, were dissected carefully to expose the variations in the venous drainage of their middle lobes. After identifying the pulmonary veins for each lobe, middle lobe vein (MLV) drainage patterns were followed to their openings. The diameters of the MLV and its lateral and medial parts were measured with a caliper. The length of the MLV trunk was also evaluated. Results: Five different types of venous drainage patterns were observed. Type-L Union of medial and lateral parts to form MLV as a trunk and opening of this vein to the right superior pulmonary vein (RSPV) (53.3%). Type-II: Opening of medial and lateral parts to the RSPV separately (16.6%). Type-III: Union of medial and lateral parts to form the MLV trunk and opening of this vein into the left atrium (16.6%). Type-IV: Opening of medial and lateral parts into the left atrium separately (10%). Type-V: Union of medial and lateral parts to form MLV trunk and opening of this vein to the right inferior pulmonary vein (3.3%). Conclusion: The venous drainage patterns of right middle lobe reveals great number of variations. Knowing the frequency of different types of drainage patterns classified in this study is extremely important for the surgeons performing pulmonary surgery, atrial fibrillation and imaging techniques. (C) 2002 Elsevier Science B.V. All rights reserved.