The paper represents an attempt to look at mental health and mental illness of migrant labourers in Western Europe in the context of their social background, current developments and the global processes they are involved in. Rates of mental illness among migrants are lower than would be predicted on the basis of the severity of the stress they face. Two facts--coming mainly from a peasant origin and perceiving themselves as peasants-in-town--were singled out as central aspects to the understanding of their capacity to cope with the stress due to migration. The main theories about migration are critically reviewed. It is suggested that peasants' strategies of survival in hostile environments underlie the explanation of the unexpected lower rate of mental illness. Phenomena of mental disturbances specific to the group are described and related to social and historical perspectives.