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cial to the survival of young, and concluding that care is always favored under selection is easy. Nevertheless, in 1994 alone, over 150 scientific papers listed in BioA6str~cts (weighted heavily toward birds) explored some aspect of parental care, belying the apparently simple proposition that this behavior is already well understood. Moreover, parental behavior is one of the most variable traits known: variation exists at all levels among taxa, populations, the sexes and individuals. How can we understand this variation? There is perhaps no more popularized aspect of animal behavior than the things parents do for offspring. Yet our understanding of the evolution of care is only rudimentary, perhaps because parental behavior is one of the most variable behavioral traits we know. Sexual reproduction, particularly in anisogamous species, has a major impact on variable patterns of care. Recent work on conflicts between the sexes over care and the consequences of variable paternity on paternal care has generated fascinating new ideas about the evolutionary forces acting on parenting.