Many studies have found start-up size of a firm to be an important determinant of its subsequent performance and probability of survival. The aim of this study is to investigate the determinants of average plant start-up size in 51 four-digit Turkish manufacturing industries for the period 1993-1999. The results of the study suggest that while industry characteristics such as industry growth rate and capital intensity have a positive impact on the average plant start-up size, industrial concentration, import penetration, and the change in research and development expenditures are negatively associated with the same variable. In addition, the macroeconomic environment is also an important determinant of the choice of plant start-up size. Finally, we find evidence that may indicate 'following' (herd) behavior in Turkish manufacturing industries.