The ovaries (each 25mm in length) of a female harbor porpoise, Phocoena phocoena, accidently caught in a set net on 26 April 2004, were examined histologically to assess their degree of maturity. The sectioned cortical region was occupied entirely with numerous primordial and primary follicles, whereas in the medullary region a small number of secondary follicles, thick-walled arteries and thin-walled veins were apparent. A few atretic follicles were also encountered. However, more developed follicles, such as Graafian follicles, were not detected. No secretory substance could be demonstrated in the mucous epithelia of the oviduct and underdeveloped uterine glands. The specimen appeared to be an infant owing to its very immature ovarian architecture.