Migration movements to industrialized countries have grown in number and size, and the presence of large numbers of immigrants has raised concerns about their integration and assimilation into host societies. This article is an empirical study of assimilation of foreign nationals in Germany. Their experience may hold lessons for other relatively recent immigration destinations. As expected, language is one of the most critical factors for determining integration and assimilation at the workplace and in society. Our results indicate uneven success in these two areas, and suggest that greater language skills may be required for social assimilation, compared to economic assimilation. Among the most important findings of our study are the strong and statistically significant effects of the attitudes by Germans toward immigrants, the significant influence of the region of residence, and the ambivalence of German-born foreign residents toward naturalization and continued stay. This signals the failure of past integration and assimilation policies. The results show that negative attitudes by ethnic Germans against others at work or in society, in general, reduce interest in integration and assimilation. This is neither new nor surprising and this research does not contribute new theoretical insights, but it demonstrates the magnitude and significance of the effects. The question of why different locations seemed to have different impacts on citizenship aspirations is beyond the scope of this article. The data do not provide information to pursue this question and we suspect that the causes are too complex for a short answer. As expected, non-EU citizens showed greater interest in acquiring German citizenship than EU citizens. Finally, the results also indicate that the immediate post-World War II notion of “guest workers” was not completely false. There has been significant return migration and a significant number of respondents to the survey say that they intend to return.