Although there is a growing literature on the factors associated with the length of interorganizational relationships, there seem to be few empirical studies related to the subject in project-based industries such as construction. In this study we looked for correlations among the length of the relationship between main and specialist trade contractors, control methods and the number of rival speciality contractors in the Turkish construction industry, drawing on the data provided by a study of 27 specialist trade contractors. Correlation analysis was used to investigate the relationship. The results demonstrate that the length of the relationship between main and speciality contractors is inversely related to the number of rival specialist trade contractors, but directly related to the flexibility of control exercised by the main contractor.