A study is described on the interference of bilirubin with the determination of creatine in serum using three automatic analysers i.e. the Technicon Chem-1, the DuPont Dimension and the Baxter Paramax. In all instruments a kinetic Jaffé reaction is applied. As comparison method we used a HPLC based selected method. All methods proved to be sensitive to interference, the Paramax showing the best performance with our set of specimens. Results regarding modifications leading to improvement and possible future experiments are discussed.