In this study, it was aimed to investigate physical and chemical interferences for different devices and methods commonly used in environmental studies. In experiments carried out with spectrophotometer, physical interference,caused from colour was investigated for phenol, ammonium, cyanide. nitrite and fluoride analyses. It was observed that colour caused deviations of 23.20, 35.07, 40.35, 279.38 and 125.00 % for phenol, ammonium, cyanide, nitrite and fluoride, respectively. The interference of sulphate was also examined in sulphide analyze. by using spectrophotometer. Results were found 40 times more because of sulphate interference. In experiments carried out with flame atomic adsorption spectrophotometer and inductively coupled plasma (ICP) interferences of metal ions were investigated in different matrixes. Furthermore by using conventional method, interference of chloride was examined in chemical oxygen demand (COD) determination. Chloride caused deviations after 500 mg/L in experiments carried out with various chloride concentrations.