A number of reports have suggested that the oxidative state of human albumin in serum and in some body fluids is associated with cell damage. However there are no reports on the redox state of human follicular fluid (FF) and its influence on oocyte viability. The aim of this study was to examine the relationship between the redox state of FF and serum on oocyte viability. The cytoplasmic condition of oocytes was evaluated microscopically at collection in 117 women. Deteriorating oocytes were recognized by degenerative changes in their cytoplasm. The redox state of FFs that yielded degenerated oocytes was evaluated and compared with fluids containing normal oocytes. The redox state of the corresponding FF and serum, at the time of oocyte retrieval, was analyzed by high performance liquid chromatography. The redox state of FF that contained degenerated oocytes was found to have a significantly elevated oxidized state compared with the FFs that yielded normal oocytes. Also the albumin in the FF of patients was found to be predominantly in the reduced state compared with that in their serum at the time of oocyte retrieval. In addition, increasing age and endometriosis were found to shift the redox of serum to the oxidative state. We propose that the reduced state of albumin in FF may play an important role in protecting oocytes from oxidative damage.