This paper evaluated the influence of point source and flow events on inorganic nitrogen fractions at 17 sites of Taechung Reservoir during 1993∼1994. Total nitrogen (TN) averaged 1.53 mg/L during the study and ranged between 0.70 and 2.56 mg/L. Dissolved inorganic nitrogen (DIN) accounted for > 90% of TN regardless of season and location, indicating a nitrogen-rich system showing eutrophic∼hypereutrophic conditions. Some 67∼94% of DIN was NO₃-N, whereas mean level of NH₄-N was less than 5% of DIN. During monsoon 1993, dilution of NO₃-N was evident in the headwaters as a result of mixing of lake water with rain water, while NH₄-N increased> 100% compared to the premonsoon. Values of NH₄-N had a positive correlation with rainfall (r = 0.85; p < 0.001) and negative correlations with theoretical water residence time (r = 0.90; p < 0.001) and conductivity (r = -0.78, p < 0.001), respectively. These outcomes suggest that NH₄-N came from external input from the watershed during the monsoon. In both years, mean TN was greater in the mid-lake sites than any other sites. A great amount of TN in the midlake was most pronounced in monsoon 1994 because of an accumulated influence of the point sources during low inflow. Overall data suggest that concentrations of TN in this system did not show large differences along the longitudinal gradients and its distributions is likely determined by point-sources rather than inflow regime.