In this study we investigated the protein expression patterns during human oocyte in vitro and in vivo maturation (IVO) by single-cell quantitative proteomic analysis of 36 human oocytes. Among 2,094 proteins quantified in 34 oocytes (GV: 11 oocytes, IVM: 12 oocytes, IVO: 11 oocytes), 224 were differential between IVO and GV oocytes during in vivo maturation, and 61 between IVM and IVO oocytes.