This paper analyzes the determinants of language abilities of migrant workers and the impact of language proficiency on their earnings position. The analysis is based on data for West Germany. The first part presents an ordered probit analysis of the determinants of German speaking and writing fluency for both male and female migrants. The data allow not only to consider personal characteristics of the migrant as explanatory variables, but to analyze additionally the effect of the family context and of illiteracy on the migrant's German language fluency. In the second part, the effect of language on the migrant's earnings position is analyzed. It is shown that language abilities, and especially writing proficiency, considerably improve the earnings position of migrants.