This study is to investigate extensively the complaint responses of the public library users, as an example of the complaining behaviors of the clients in not-for-profit organization. It selects and analyzes empirically some of the antecedents of the complaining behaviors including attitude toward complaining, cost of the complaining, likelihood of success, of success, product, external attributions and loyalty, and complaint responses including exit, voice(redress seeking), negative word-of-mouth and third party complaints, of the public library users, based on the theoretical backgrounds. It also examines the free use as a new variable of antecedents for not-for-profit organizations. Final data through questionaries are obtained from 515 unsatisfied adult public library users in Taegu, 456 of them analysed with SPSS 10.0 for Windows.