The molar extinction coefficients for p-nitrophenol at pHs in the region of 8.0-9.2 in the present, 2 and absence of various additives were determined. The data were statistically analysed. The validity and reproducibility of these values were discussed. The study reveals that pH has a considerable effect on molar extinction coefficient values. These values are however not influenced by such additives like cetyltrimethyl ammonium bromide (CTAB), various strength of carbonate-bicarbonate buffer and potassium bromide at the same pH.