This paper presents the experimental results in five months operation from a combined anaerobic/oxic system treating swine waste with average concentrations in organic matter and nitrogen of 7,930 mgCOD/L and 671 mgTKN/L, respectively. The system was formed using an upflow anaerobic sludge blanket (UASB) reactor and oxic reactor connected in series with a recycling line of oxic effluents to UASB for its denitrification. The UASB reactor was operated at an organic volumetric loading rate (VLR) of $2.1{sim}4.5;kgTCOD/m^3$/day and the removal efficiency of TCOD was $66.3{sim}85.4%$. The overall removal efficiency of TCOD was more than 99%. The oxic reactor was operated at a nitrogen VLR of $0.10{sim}0.20;kgTKN/m^3$/day and the nitrification efficiency was 75%. However, the complete denitrification was observed in the UASB reactor that was due to the optimal temperature and sufficient carbon source. The overall removal rate of TN was about 80%. About 76.2% of the influent COD mass was accountable in a COD mass balance at a level of VLR $3.64;kgCOD/m^3$/day. The production rate of methane was $0.32;LCH_4/gCOD_{removed}$ when influent organics, VLR, were recorded by $3.4{sim}4.5;kgCOD/m^3$/day.