Clinical chemists frequently encounter hemolyzed samples. Our study examines the effects of hemolysis on the results of 25 common biochemical tests. We collected 60 15-mL blood samples from inpatients and outpatients and mechanically hemolyzed 10 mL of the samples in a two-step procedure. We classified serum from these samples as being nonhemolyzed, moderately hemolyzed, or severely hemolyzed and then performed 25 common biochemical tests. Statistical analysis of the results showed that hemolysis had the greatest effect on the lactate dehydrogenase, acid phosphatase, and potassium tests.