[2] The genus is found from Mexico to Tierra del Fuego and includes approximately 17 species.

[3] In Argentina and Chile, Oligoryzomys longicaudatus and other members of the genus represent the reservoir for the hantavirus strain Andes virus (ANDV) (Wells et al., 1997; Levis et al., 1998; Cantoni et al., 2001).

More recently, molecular analysis and morphological data has placed the genus in Clade C, alongside Neacomys, Microryzomys and Oreoryzomys.

They differ from Oryzomys in being mostly terrestrial rather than semi-aquatic and in having longer tails in proportion to their body size.

[6] Some species such as O. flavescens[8] and O. longicaudatus[9] are the principal reservoir host of certain hantaviruses which are harmless to rodents but can cause disease in humans.