This article reports the results of a research about the sustai-nability of extractive farmers in the Atlantic slopes of Rio Grande do Sul. The extractive economy at issue is related to a species usually known as leather fern (Rumohra adiantiformis (G.Forest.) Ching). It is estimated that 3,000 families in the region perform this non-regulated activity, whi-ch is their only source of income. The sustainability degree of farmers was calculated from information related to environmental, social and eco-nomic dimensions, and to productivity, stability, equity, resilience, and autonomy criteria. The analysis focused on the comparison among the In-dexes Related to Dimension (IRD), Criteria (IRC) and Sustainability (IRS) of each kind of production system. The results pointed to the existence of four kinds of production systems, and three of them were included in this research. The sustainability indexes showed that the production system type 3 was the most sustainable, followed by type 2 and, fi nally, type 1.