This chapter presents a case study examining the patterns and determinants of firm-level investment in the Turkish economy after the opening of capital account in 1989. It does so by ‘mixing’ quantitative firm-level data with qualitative insights from fieldwork. Semi-structured interviews with firm mangers are used to explore the determinants of investment and generate a framework of investment in the context of a highly volatile macroeconomic environment. Then quantitative data and econometric methods are used to assess whether the framework emerging from the qualitative part is valid. Qualitative results pose a challenge to various assumptions of neoclassical investment models and give support to post-Keynesian insights about managerial decision-making and investment behavior. Quantitative data and analysis confirm these qualitative findings, and lead us to others than can be better understood by insights from fieldwork. For instance we see that internal funds are an important determinant of investment; yet a priori categories, such as size or age, are not useful predictors of financing constraints for investment.