Side by side measurements of NPOC concentrations in drinking water samples using two high temperature combustion oxidation (HTCO) instruments, Shimadzu TOC-5000 and Dohrman DC-190, and an ultraviolet persulfate (UVP) instrument, Dohrman DC180. the NPOC concentrations of the samples agreed to within 14% of the average of the three instruments for each sample. The recovery percentage of a 1.0 ppm potassium hydrogen phthalate (KHP) spike averaged for all samples on each instrument was TOC-5000 = 102.8 plus or minus 2.3%, DC-190 = 87.0 plus or minus 26.9%, and DC-180 = 131.9 plus or minus 29.5%. The results indicate that the HTCO instruments can accurately and precisely analyze drinking water samples.