Porous polyethylene (Medpor) is an alloplastic material worldwide used for craniofacial reconstruction. To evaluate complications and risk factors associated with this synthetic graft, a retrospective study was performed. A series of 285 Medpor grafts were placed in 187 patients. Age, sex, diagnosis at admission, site, type of surgical insertion, type of fixation, and outcome (no complications, anesthesia, exposure, infection, and implant remodeling and removal) are considered. By means of univariate and multivariate analyses, we detect variables most associated with poor outcome. Univariate analysis showed that graft "survival" curves stratified according to (1) diagnosis at admission and (2) site are statistically significant. Subsequently, a Cox analysis was performed: both variables are also predictors of graft outcome. Porous polyethylene is a reliable alloplastic material that can be satisfactory used for craniofacial reconstruction. However, some sites (i.e., nose, maxilla, and ear) and diagnosis at admission (i.e., syndromic patients previously operated) are related to an higher risk of implant failure.