A method was devised with the purpose of preparing significant amounts of isolated intact follicles suitable for "in vitro" studies on the protein synthesis machinery of mammalian oocytes. Ovaries of immature mice(8-14-days old), free of annexes and surrounding fat are squashed gently on a wire screen placed over the rim of a centrifuge tube. This step is followed by washing the screen in a saline-gelatin solution which is centrifuged twice at low speed to separate intact follicles from smaller ovarian components. At the mentioned ages about 170-190 follicles of 80 mu in diameter are found in the ovary. 20% of this population comes out intact from the screen which means that 30 ovaries may yield about 1,000 free follicles. The samples were examined under the light microscope to check their homogeneity and in the electron microscope to see whether squashing introduced changes in the cell cytoplasm. No significant changes were observed. This method is therefore considered useful as a previous step to studying, at the molecular level, the metabolic phenomena related to oocyte growth and further differentiation.