Polyandry and sperm competition have strong impacts on the evolution of animal mating systems but have been ignored in studies of anurans. Polyandry occurs in many forms in frogs, occurs in seven families and is particularly common in the Rhacophoridae. Anuran polyandry is commonly associated with high male bias at breeding sites, but females may also deliberately solicit matings with multiple males. Comparative data sets demonstrate clear effects of polyandry on the evolution of testes size and sperm morphology, and similar patterns occur within species. There is experimental evidence of compatibility effects and that sperm-egg interaction patterns are affected by egg and ejaculate properties. We speculate about the role of polyandry in the evolution of anurans; e.g. impacts on strategic ejaculation and sperm storage organs, on body size, call structure, and anuran diversity. Our review is built around an extensive literature on polyandry in the Australian Myobatrachid frog Crinia georgiana. © 2011 Elsevier Inc.