This study analyses the startup companies attending business accelerator programs in Turkey. Business accelerators are new generations of incubation programs born especially to support technology entrepreneurs and help them reach to the next level. This study makes a research on eight accelerator programs located in Turkey. Using a survey developed for entrepreneurs attending these accelerator programs, this study provides an inside look into the effectiveness of these programs from the perspective of startup companies. The main goal of this study is analysing how startups use the services provided by the accelerator program. According to startups employee size, average monthly turnover and exportation status, several hypotheses have been identified for measuring the effectiveness of supports provided in these accelerator programs. The data of this study have been analysed via SPSS and it contributes to the literature by analysing accelerator supports and services so that accelerators can differentiate their programs according to the needs of the startups.