Here we offer a brief introduction to this special issue on argument-encoding systems of the little-known languages of Bolivian Amazonia, a region extremely rich linguistically. After providing some information on the sociolinguistic settings and the history of linguistic research in this area, we focus on the domain of argument-encoding systems in those languages and show how very diverse types of systems are found in languages spoken in very close proximity, including hierarchical/inverse cross-referencing systems, ergative systems, and split-intransitive systems. We also point to a number of typologically and theoretically interesting phenomena found in these languages, such as fluid transitivity, double-object ditransitive constructions, and rare valency-changing derivations such as multiple applicatives and sociative causatives.