The numbers of cases of high level of serum lactate dehydrogenase (LDH) found in the mass screening program by Naganoken Koseiren Kenkokanri Center was 1, 358 (1.5% of total 89, 837 examinees) in 1995. In 235 of these cases, 141 cases (60.0%) were diagnosed as normal; 56 cases (23.8%), hyper lactate dehydrogenasenemia; 27 (11.5%), diseases of the liver or gallbladder. Close medical examinations including abdominal ultrasonography and check on viral hepatitis may be necessary for cases of increased LDH levels detected by mass screening.