The fathead minnow, Pimephales promelas Raf., presents a classical model of teleostean embryogenesis. Its prehatching development has been divided into 32 stages, each representing an easily observed interval in the developmental continuum. Embryos were examined live and histologically under controlled laboratory conditions. Fertilization, early cleavage, epiboly, and organogenesis are very similar to that of other cyprinids except for the tiiming of the appearance of specific structures. Hatching was found to occur in approximately 120 hours post-fertilization at 25 degrees celcius. Rapid embryonic development, coupled with a short generation time of 3-6 months under laboratory conditions, make it a useful native North American species for studies in experimental embryology.