I am pleased to contribute to this special issue of Biology of the Cell in honor of Yoshio Masui. Oocyte maturation remains a small enough and young enough field that the authors assembled for this issue can trace the entire development of the field over the last 30 years, beginning with the early demonstration by Masui (1967) and others, that steroids can induce complete maturation of denuded oocytes in vitro. Not very long after that Masui and Markert (1971) published the seminal paper that identified MPF and CSF activity. In this article I intend to highlight recurring themes in oocyte maturation that continue to be actively investigated, almost all of which derive from studies pursued at some point in time by Masui and his colleagues.