Polycystic ovarian syndrome is a hetrogenous condition with a broad clinical and pathologic spectrum that may reflect the effects of diverse etiologic factors. Polycystic ovarian syndrome is an abnormality in the maturation of the follicles which can result in abnormal composition of FOLLICULAR FLUID. By analysis and comparison of the biochemical composition of human FOLLICULAR FLUID in normal and polycystic ovaries, we undertook to find the etiology of arrested FOLLICULAR development in this syndrome and to gain an insight into the role of biochemical constituents of FOLLICULAR FLUID on FOLLICULAR development.The results of our study indicate hiher concentration of potassium, lower concentration of testosterone and higher level of pH in normal ovaries relative to polycystic ovaries. In conclusion, potassium and testosterone concentrations and pH level seem to be some of the most important factors in the oocyte maturation and the acquistion of FOLLICULAR development; and changes in them may have important role in the etiology of polycystic ovarion syndrome.