In explaining variability in tropical deforestation, scholars of land use/cover change (LUCC) have focused almost exclusively on in situ (or “on-farm”) resource use, while population researchers have largely ignored rural-to-rural migration. The way in which household responses to the human and physical environment in one place may affect land cover change in another place has been inadequately explored. This paper investigates the primary proximate and underlying causes of deforestation in the humid tropics with a case study from Guatemala. To investigate the first cause of this phenomenon, farmer land use, I collected data from community leaders in twenty-eight communities and from 279 settler farmers and 221 women in nine communities in the Sierra de Lacandón Park (SLNP). To address the second cause of deforestation in the SLNP, migration, I conducted interviews with community leaders in twenty-eight communities of SLNP settler origin. Results from the SLNP revealed several factors positively related to forest clearing at the farm level including family size, secure land title, duration on the farm, agricultural intensification , ethnicity, and farm size. Results from areas of origin of migrants suggest that many of the same factors contributing to variation in deforestation at the household level in the SLNP are also linked to migration to the frontier in the first place. Larger families, Q’eqchí Maya, landless households, families with small or environmentally degraded plots, households with poor access to labor and produce markets, the least educated, and the exceptionally poor run the greatest risk for migration to the frontier. Evidently, attention to both migration origin and destination areas enhances options for policy interventions aimed at sustainable rural development and forest conservation