Rubber is the most widespread smallholder tree crop in Southeast Asia. Some analysts have blamed the expansion of rubber for greatly contributing to the conversion of mature tropical forest in both Indonesia and Malaysia. The paper critically examines to what extent smallholder rubber production actually led to forest conversion in West Kalimantan (Indonesia) and neighbouring Sarawak (Malaysia). The paper concludes that the introduction of rubber in West Kalimantan contributed little to encroachment into primary forest. Rather, it apparently favoured the restoration of forests in areas where land use became less intensive. This happens only where specific conditions in the local context allowed this to take place. The findings suggest that tree technologies should be preferred when trying to improve local agriculture. Incorporation of local resource management technologies, especially tree planting or forest management technologies, may enhance positive outcomes in terms of increased income and forest preservation.