It is an important issue in the software industry to predict how much effort will be required for a software project. The more accurate the effort estimation is in the early product development lifecycle, the higher is the performance in utilization of the resources and the in meeting the deadline requirements. There are some numbers of methodologies developed for effort estimation. Use Case Points (UCP), which is used for extracting and defining the functional requirements of a software system, is very popular and widely used effort estimation methodology both in the industry and academia. In this study, we evaluated effort estimation in thirteen software projects. Seven of thirteen projects are taken from a CMMI level 3 certified defence industry company. The remaining projects are taken from Heltewing's dissertation . We calculated the effort of software projects according to Karner's UCP method, by fixing the Technical Complexity Factor (TCF) and Environmental Factor (EF) to one. According to results we obtained, taking the TCF=1 gives a higher correlation between the actual effort and estimated effort than the correlation obtained regular UCP method applied.