Our study design consists of three parts. First, we extracted 300 rejected patches from the development history of Eclipse and Mozilla, and manually inspected their patch review comments to understand why they were rejected. Second, we conducted a large-scale online survey involving 246 Eclipse and Mozilla developers. From this online survey, we mainly investigate reasons that are the most decisive for rejecting a patch. We further surveyed the past literature on patch review to complement the empirical results of our manual inspection and developer survey.