This paper analyzes technical efficiency of limited-resource farms operating in a sub-tropical environment (Province of Misiones, Argentina). Property rights over land, the degree of market exposure and food support programmes are three institutional variables that are hypothesized to lead to departures from the production frontier. Econometric analysis indicates that market exposure and receipt of food transfers increase efficiency. No effect of land ownership is detected. We argue that slash-and-bum agricultural systems allow non-owners of land to operate as or more efficiently than landowners.