This compendium of the katydids of Argentina and Uruguay is still in progress. Almost all of the species known to be present are listed. Some old and doubtful records were discarded, and a few others are still under investigation and not yet included. Observations from our own fieldwork will be added constantly. So far very little is known of most species, but we are working on providing brief information on biology, ecology, and especially completing distribution data. Contributions, especially good photos and new photographic records for particular provinces, as well as comments, are welcome (see our e-mail addresses below). Sometimes a specimen is necessary for a reliable identification, and if possible, we would be happy to receive live individuals, to record the males’ calling songs, which are still unknown for most of the species.