AbstractWe evaluated an immunoturbidimetric quantitation for serum myoglobin by the latex agglutination method using an automated biochemical analyzer. This method is rapid, specific, accurate, precise, and has wide dynamic range. The total assay time is 10 min and is performed at 37°C with continuous monitoring at 570 nm.The assay results were compared with radioisotopic immunoassay results and showed a good correlation coefficient, r= 0.99; Y = 0.98× + 9.3; N = 79. Sera from healthy adults has a myoglobin concentration in the range of 15‐80 ng/ml(N=362). Sex‐and age‐related differences were observed. The serum myoglobin levels in males and elderly people showed higher concentration than in females and younger people. The peak elevation of serum myoglobin compared with other cardiac markers was observed within 6 hours after onset of chest pain as well as the CK‐isoform ratio (MM3/MM1). All of the serum from 21 patients with definite acute myocardial infarction showed increased serum myoglobin levels (100‐1200 ng/ml) upon admission and within 6 hours.The results suggest that assays for serum myoglobin levels are helpful in the early diagnosis of acute myocardi