Among the many parameters describing water quality, total nitrogen content(T-N) is regarded as important one in relation to water quality management of the waterbodies far its role in eutrophication process. For that matter high accuracy in determining the total nitrogen content is imperative. Furthermore, Korean government put under the regulation the total nitrogen contents of the effluent from the wastewater treatment plants since 1996. Two methods are commonly used to determine the total nitrogen contents. One is based on the oxidation of all the nitrogen in the sample to nitrate with potassium persulfate under alkaline conditions being followed by spectrophotometric measurement with UV light of 220 ㎚ wavelength. The other is based on the separate determinations of the organic nitrogen, ammonia, nitrite, and nitrate being followed by summation to obtain total nitrogen contents. The two methods are studied for comparison. Following conclusions are made from the study. 1. The UV spectrophotometric method after oxidation appears to be more convenient and accurate in determination of the T-N contents than the summation method after separate determination. 2. The UV method suffers of the interference by Cr(VI) and bromide ions so that it cannot be recommended for the samples of sea water. 3. The interference of carbonate ions in the oxidized sample to the UV method can be overcome by adjusting the pH of the solution to be between 2 and 3. 4. The UV method seems to be more favorable in sense of time-saving and labor-saving. 5. For the determination of T-N, the UV method appears to be superior than the summation method. But summation method turns out to be indispensable in studying of the transformation of nitrogen species in the aquatic environment or in the water treatment processes.