The argument that environmental degradation is an important driving force of migration has experienced a strong revival in the climate change context. While various studies predict large environmental migration flows due to climate change and other environmental stressors, the ex post empirical evidence for such migration is very patchy at best. We contribute to the emerging empirical literature in this field by focusing on the micro-level. We examine how and why different types of environmental conditions may lead to internal migration. The analysis relies on survey data for both migrants and non-migrants in 12 countries. The results suggest that while long-term environmental events, such as droughts, have no significant effect on internal migration, sudden-onset environmental events in the form of floods significantly increase the likelihood of migration. Furthermore, individual perceptions of negative environmental conditions can motivate people to move. We also find that people tend to respond to long-term environmental problems, such as environmental degradation, with adaptation, rather than migration. These findings indicate that different types of environmental problems – notably, natural hazards vs. gradual environmental degradation – can create different incentives for people to migrate or stay.