Clinical usefulness of Essential Laboratory Tests (1), proposed by Japan Society of Clinical Pathology, was retrospectively evaluated in 500 outpatients who first visited the medical clinic of a prefectural general hospital. Sixty percent of the patients were diagnosed with gastrointestinal disease or respiratory disease. Performance rates of urinalysis, blood counts, serum total protein, A/G ratio, C-reactive protein, erythrocyte sedimentation rate and fecal occult blood were 87.6%, 55.8%, 49.6%, 48.8%, 37.8%, 10.0% and 5.6%, respectively. Abnormal test results rate of urinalysis, blood counts, serum total protein, A/G ratio, C-reactive protein, erythrocyte sedimentation rate and fecal occult blood were 12.3%, 12.9%, 14.1%, 5.7%, 21.6%, 22.6% and 25.9%, respectively. The clinical diagnoses and the abnormal test results indicated that the patients general condition was assessed properly from the A/G ratio, 92% of patients with proteinuria were transient cases and urobilinogen has poor sensitivity and specificity for the diagnosis of liver diseases.