The zona pellucida of vitellogenic oocytes of the Brazilian White Piranha (Serrasalmus brandtii) is composed of three layers traversed by radial striae which can be differentiated by cytological and cytochemical methods. Its formation begins in oocyte 2 (previtellogenesis), with the development of the outer layer. The middle layer is formed during vitellogenesis and the inner layer--which accounts for most of this envelope--in the fully vitellogenic oocyte. The chemical nature of each layer can be determined by cytochemical techniques for carbohydrates and proteins. The origin of the teleost zona pellucida is discussed.