A modification ofthe wellknown creatinin-PAP method was evaluated. The obtained precision andaccuracy of the new method was good. The procedure is a reliable method for the determination of creatinine concentration in serum and urine. No interference from bilirubin (up to 1100 / ) and drugs were detected. A slight negative effect of haemolysis (haemoglobin > 2,0 g/i) was noticed.