The aim of this study was to investigate the biological treatability of fruit juice industry effluents in Sequencing Batch Reactor (SBR) and Activated Sludge Reactor processes. The characterization of the wastewaters can be summarized as follows: 1000-1500 mg/L of COD, 3.3-6 mg/L of TKN, 0.104-0.19 mg/L of TP for sour cherry juice industry and 2500-4500 mg/L of COD, 95-115 mg/L of TKN, 12-28 mg/L of TP for apple juice industry. In the study, a lab-scale sequencing batch reactor (SBR) and an activated sludge reactor with liquid volumes of 4 L each were used. The SBR and activated sludge reactor were operated with a cycle time of 12 and 24 hours, respectively, at aerobic conditions. Both reactors have been observed for 300 days. 90-95% of soluble COD removal was achieved by biological treatment in both of the reactors. In addition to the biological treatability studies, microbiological investigations were performed, and kinetic and stoichiometric coefficients were determined. The kinetic and stoichiometric coefficients for sour cherry juice wastewater are as follows: maximum specific growth rate (μ̂m): 5.15 d -1, endogenous decay rate (bH): 0.32 d-1, and biomass growth yield (YH): 0.53 g MLVSS/g COD. The kinetic and stoichiometric coefficients for apple juice wastewater are as follows: maximum specific growth rate (μ̂m): 6.18 d-1, endogenous decay rate (bH): 0.13 d-1, and biomass growth yield (YH): 0.62 g MLVSS/g COD. According to the microscopic examinations, excessive growth of fungi was observed. This observation was attributed to the characteristics of the wastewater. However, such a growth did not cause any adverse problem on treatability.