I use linked employer-employee data from the German Federal Statistical Office to estimate within-firm wage differentials between temporary workers with fixed-term contracts and workers with permanent contracts in the context of dual internal labor markets. Wage-tenure profiles of permanent workers are estimated separately for each firm to obtain a proxy for the prevalence of internal labor markets. Temporary workers earn significantly lower wages in firms with steeper wage-tenure profiles. This finding is consistent with the segmentation in a primary permanent workforce with high wages and a secondary temporary workforce with low wages, if internal labor markets are more prevalent.