In December 2009 the EUROPLANET Research Infrastructure, a project funded by the European Community under the Capacities programme of the Seventh Framework Programme (grant agreement number 228319) and the International Space Science Institute, organized a workshop in Bern to overview and summarize our current knowledge on the plasma environments of Venus, Mars, and Titan. This was the first workshop organized in the series of four planned in the networking activity NA-2 of Europlanet RI. Emphasis was on new results, since many excellent reviews were published recently. The comparison of the plasma environment of these three solar system objects was a primary focus of the workshop, which also aimed at defining directions for future research, through further use of existing data or development of new space missions. In this introductory paper, we summarize the main results of this workshop, via an overview of the different chapters it contains. Unlike the Earth, our neighbours Venus and Mars have no global magnetic fields, although Mars has small-scale crustal fields; and Titan, to our best knowledge, is also a nonmagnetic body. These three objects are the only non-magnetic solar system bodies having a dense atmosphere. Venus and Mars have the supersonic and super-Alfvenic solar wind as their plasma environment. Titan, in contrast, is located inside Saturn’s hot, rapidly rotating, subsonic, multicomponent magnetospheric flow (although it occasionally makes excursions into the magnetosheath) and its environment is highly variable in time. Accordingly,