Effect of closing dead space on incidence of seroma after mastectomy. Seromas are a significant cause of morbidity after modified radical mastectomy. The effect of closing dead space by suturing skin flaps to underlying muscle combined with early removal (48 hours postoperatively) of closed suction drains on formation of the seroma was evaluated prospectively in 37 patients. Thirty-three underwent modified radical mastectomy for invasive carcinoma while four underwent total mastectomy with a level 1 axillary dissection for multifocal intraductal carcinoma. Seromas occurred in three, all were minor, two required one aspiration only and one required two aspirations. Two were seromas of the lower flap while one was an axillary seroma. Except for one patient who had a wound hematoma develop, no other instances of morbidity were noted. Closing dead space by suturing skin flaps to underlying muscle combined with early removal of closed suction drains is associated with a low incidence of seroma formation after mastectomy. Use of this technique has important economic and clinical implications for patients who had mastectomy. 