Parental care characterizes the reproduction of the brown bullhead Ictalurus nebulosus. In nature, relatively few broods survive to the normal termination of parental care. Most mortality occurs early. Fishes, including conspecifics, consume bullhead eggs and young, and potential predators that approach a brood are frequently chased by an attending parent. Minnows and sunfishes are the most frequent intruders at nests. In addition to chasing intruders, parents prepare a nest site before oviposition, fan eggs and larvae and manipulate the egg mass orally. When both attending adults were experimentally removed from their egg mass, broods always failed to reach the larval stage of development. Most of these egg masses disappeared shortly after the parents were removed and before the larval stage of development was reached in control broods. This suggests that predation was a major source of brood mortality occurring in the absence of adults. However, in the absence of predation or when predators were excluded from an egg mass, all embryos still failed to survive to the larval stage of development. The risks of fungal infection and insufficient gas exchange are important factors in the maintenance of parental care, and all of these factors may have been important in the evolution of care-giving behavior.