Abstract The quantitative and qualitative aspects of protein synthesis during Xenopus oocyte maturation were investigated. Progesterone or the injection of maturation promoting factor (MPF) both increased protein synthesis approximately twofold relative to controls. However, MPF induced a precocious increase relative to the time of germinal vesicle breakdown compared to that observed in response to progesterone. Examination of two-dimensional gels showed minimal changes in the types of polypeptides synthesized from control and progesterone- and MPF-matured oocytes. Rather there was an overall increase in the synthesis of individual polypeptides during progesterone and MPF-induced maturation.