m.3243A>G mutation in mitochondrial DNA is the most common pathogenic point mutation, causing a variety of phenotypes. To further elucidate its clinical characteristics, we recruited 47 Chinese families carrying m.3243A>G mutation and analyzed their symptoms, disease history, inheritance, and mitochondria-related complications. In the probands, lactic acidosis, myopathy, seizures, short stature, weight loss and hirsutism were the most common clinical features. In their mothers, lactic acidosis, exercise intolerance, short stature and weight loss were the frequent manifestations, and normal phenotype was found in 59.6% mothers. m.3243A>G mutation was detected in 47 probands and 42 mothers. In the probands, the mutation ratio in blood was threefold higher and the ratio in urine was twofold higher than those of their mothers. m.3243A>G mutation ratio in mothers' urine and in their probands' blood were weakly correlated. In conclusion, (a) stroke-like episode induced by m.3243A>G mutation may be the symptom predominantly found in older patients; (b) m.3243A>G mutation ratio correlates with the severity of the disease; (c) m.3243A>G mutation ratio in mothers' urine may correlate to the ratio in blood in their offspring. (C) 2010 Elsevier B.V. All rights reserved.