Foot-and-mouth disease (FMD) can lead to myocarditis in young animals, but the age distributions of calves with myocarditis have not been described, nor the biochemical profile in these calves. In an area endemic with foot-and-mouth disease, calves less than 6 months of age in infected farms were examined for clinical lesions and abnormalities in respiratory rate, heart rate and heart rhythm. In total, 53 calves were identified to be suspected of having foot-and-mouth disease infection. In 6 calves myocarditis was suspected based on tachypnea, tachycardia and gallop rhythm. In these 6 calves, cardiac troponin-I (cTnI) and aspartate aminotransferase (AST) were significantly higher (P<0.0001), but the levels of Creatinine Kinase MB (CK-MB) and Lactate dehydrogenase (LDH) were not. These 6 calves died within 2 days and histopathology confirmed myocarditis. All calves with myocarditis were younger than 2-months old, suggesting that myocarditis caused by FMD is mainly found in very young suckling calves.