This is a level one, prospective, randomized, controlled multi-center clinical study comparing two types of acellular dermal matrices (ADMs) currently used in immediate post-mastectomy prosthetic breast reconstruction. Comparison of these two ADMs will be made in the areas of reconstructive clinical outcomes and aesthetic outcomes. Patients will be randomized into one of two ADM groups as part of their immediate post-mastectomy breast reconstruction. Patients in both groups will be followed for twelve months after their reconstructive surgery. Clinical outcomes will be documented at 1 month, 3 months, 6 months and 12 months following breast reconstructive surgery. For one-stage breast reconstruction, aesthetic outcomes will be assessed and documented at 6 and 12 months following implant placement. For two-stage reconstruction, patients will be evaluated for aesthetic outcomes at a time point 6-12 months following expander-to-implant exchange if it does not coincide with the 12 month post-mastectomy visit.