Phyletic divergences between neotropical Ranids and other South American Anurans (Leptodaetylidae. Hylidae, Bufonidae) were indicated by precipitin tests. Remarkable serological affinities between Phyllomedusa and Bufonids and Leptodactylids were discovered. The results warrant further studies on the problem of relationships between the true Hylids and the very specialized forms of the neotropical Phyllomedusa-Agalychnis stock.Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Museo