The paper presents new studies about the removal efficiencies and characterization of the Municipal Wastewater Treatment Plant (MWWTP) in Kayseri, Turkey, which is serving for 800,000 population equivalents with the capacity of 110,000 m(3)/day, between 2006 and 2009. Kayseri discharges its effluents to Karasu Creek that downstream joins the Kizilirmak river, the longest river in Turkey discharging into the Black Sea. Four years of operation data between 2006 and 2009 calendar years were obtained from KASKI General Directorate. Influent and effluent samples were collected daily and suspended solids (SS), chemical oxygen demand (COD), biochemical oxygen demand in 5 days (BOD5), total nitrogen (TN), and total phosphorus (TP) were measured, aiming to study the evolution of the removal efficiencies for each year. The following yearly mean removal efficiencies were performed in the treatment plant: 94%, 97%, 97%, 95% for SS; 94%, 96%, 95%, 95% for COD; 98%, 98%, 98%, 98% for BOD5; 84%, 87%, 89%, 82% for TN; and 71%, 86%, 80%, 86% for TP, in 2006, 2007, 2008, and 2009, respectively. The performance of Kayseri MWWTP was given both in terms of influent and effluent quality and in comparison with the current legislation on discharge limits to the receiving body. During the studied period, mean concentrations in the effluent did not exceed the imposed limits, but sometimes, higher values were noticed for SS, TN, and TP. In conclusion, the plant performances concerning these parameters were excellent and Kayseri MWWTP was operating efficiently according to the conventional control parameters.