Ravenelia is a rust fungus which belongs to the order Uredinales. The rust fungi are among a few well-studied important disease causing agents including the genus Puccinia which has created history in economy of crop production. Ravenelia is a tropical and subtropical biotrophic fungus infecting mostly members of the families Leguminosae and uphorbiaceae. The pathogens perpetuate either in autoecious form forming all the four developmental stages or in many cases only a few stages on the same host plants. The germination of teliospores has only been observed in a few cases. The author has presented a detailed account of nuclear behaviour, haploid chromosome complement in basidia and basidiospores in some species for the first time. The developmental stages of the telia and discovery of pycnial/aecial stage in the life cycle of some species is noteworthy. Natural occurrence of hyperparasites of Ravenelia species are also reported. Due to the presence of scanty literature on this biotroph, it is hoped that this book will be very useful for students, teachers and researchers working on the taxonomy, cytology and morphology of Ravenelia species.