Around the recent turn of the century, violent clashes between Madurese and other ethnic groups took place in the provinces of West and Central Kalimantan. At least 1200 Madurese were killed, with several hundred thousands internally displaced. However, in the provinces of South and East Kalimantan, which also have Madurese minorities, such eruptions of violence did not occur. To reach a better understanding of the background, conditions and causes of such ethnic violence, we have compared the relationships between the Madurese and other population groups in conflict-ridden West Kalimantan and conflictfree East Kalimantan. The comparison shows that there are significant dissimilarities between the two regions with regard to the ethnic composition of the population, cultural attitudes, access to natural resources and political competition. Together with the negative characteristics attributed to the Madurese by other groups, these can largely explain why this minority, during the recent regime change, became the target of the frustrations and aspirations of others in the western part of Kalimantan but not in the eastern part.