The theories of internalization and internationalization provide general factors of international market entry but are not precise about its timing. A model of waiting and growth options seizes the importance of flexibility to FDI decisions and centers the impact of uncertainty. The results of a panel study using aggregates of 5379 German entries to 22 countries suggest that uncertainty has a U-shaped influence on the probability of entry and a negative effect on the amount of capital whereas it leaves the share in capital unaffected. Investors seem to treat foreign subsidiaries as real options on internationalization but not on internalization.