['A prior study in patients undergoing breast surgery with and without the use of paravertebral blocks (PVB) found no significant difference in patient length of stay (LOS). However, patients undergoing bilateral procedures and those undergoing immediate reconstructions were excluded. We sought to determine if the use of PVB in patients undergoing unilateral or bilateral mastectomy plus immediate reconstruction decreases patient LOS.', 'We undertook a retrospective review of patients who had mastectomies with immediate reconstructions with and without the use of preoperative PVB. Outcomes including LOS, postoperative nausea and vomiting, and time to oral narcotics were compared between groups.', 'Mean LOS for the PVB group was 42\xa0h. This was significantly less than the mean LOS of 47\xa0h for the nonblock group (p\xa0=\xa0.0015). The significantly lower LOS for the PVB group was true for patients undergoing bilateral procedures (p\xa0=\xa0.045), unilateral procedures (p\xa0=\xa0.0031), tissue expander placement (p\xa0=\xa0.0114), and immediate implant placement (p\xa0=\xa0.037). Mean time to conversion to oral narcotics was significantly shorter in the PVB group (15\xa0h) compared with the nonblock group (20\xa0h) (p\xa0<\xa0.001). The incidence of postoperative nausea in the PVB group (42.8\xa0%) was also significantly less than in the nonblock group (54.7\xa0%) (p\xa0=\xa0.031).'] Does use of preoperative paravertebral block decrease length of stay in patients undergoing mastectomy plus immediate reconstruction?