Immunoglobulin G (IgG) is the predominant serum immunoglobulin and has the longest serum half-life of all the antibody classes. The European rabbit IgG has been of significant importance in immunological research, and is therefore well characterized. However, the IgG of other leporids has been disregarded. To evaluate the evolution of this gene in leporids, we sequenced the complete IGHG for six other genera: Bunolagus, Brachylagus, Lepus, Pentalagus, Romerolagus and Sylvilagus. The newly sequenced leporid IGHGgene has an organization and structure similar to that of the European rabbit IgG. A gradient in leporid IgG constant domain diversity was observed, with the CH1 being the most conserved and the CH3 the most variable domain. Positive selectionwas found to be acting on all constant domains, but with a greater incidence in the CH3 domain, where a cluster of three positively selected siteswas identified. In the hinge region, only three polymorphic positions were observed. The same hinge length was observed for all leporids. Unlike the variation observed for the European rabbit, all 11 Lepus species studied share exactly the same hinge motif, suggesting its maintenance as a result of an advantageous structure or conformation. ; The Portuguese Foundation for Science and Technology (FCT) supported the doctoral fellowship of A.P. (SFRH/BD/71252/2010); J.A. is supported by an FCT Investigator grant no. IF/01396/2013. This work was partially funded by FEDER (Fundo Europeu de Desenvolvimento Regional) funds through the Programa Operacional Factores de Competitividade (COMPETE programme; FCOMP-01–0124-FEDER-028286) and Portuguese national funds through FCT (research project PTDC/BIA-ANM/3963/2012)–Quadro de Referência Estratégico Nacional (QREN) funds from the European Social Fund and Portuguese Ministério da Educaçao e Ciência. ‘Genomics Applied to Genetic Resources’, cofinanced by North Portugal Regional Operational Programme 2007/2013 (ON.2—O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), supported this work. ; Peer Reviewed