Stem and twig blights caused by C. parasitica were surveyed from four to five different localities of Kyungnam-, Kyungbuk-, Chonnam-, Chonbuk-Do in south Korea. The chestnut stands were away at least 20 km from each other and consisting of more than 200 trees. Bark disks were taken with cork borer (t/J 10 mm) from above and below the canker, and stored separately in a plastic film bag. The disks were surface-sterilized with flame before isolation. Total 289 C. parasitica were isolated by morphological characteristics of the colony on PDA and PDA-MB. The isolation frequency of C. parasitica was 40. 1% in Kyungnam-Do, 32.7% in Chonnam-Do, 20.1% in Kyungbuk-Do, and 13.9% in Chonbuk-Do. Pathogenicity was examined by inoculating 5 mm mycelial plugs of each isolates on excised stems (3.5-5.5 cm thick) and incubating 5 days at room temperature. Brown-discolored areas were measured for disease severity. The areas varied from 0.5 to 4.5 cm2, whereas standard virulent- (EP) and hypovirulent-isolate (UEP) from Chonbuk University discolored 1.3 and 0.6 cm2, respectively. After 2-3 weeks of incubation, yellow perithecium-like structures broke through the bark surface of inoculated stems. Curled conidial tendrils were the only structures to recognize the presence of pycnidia on the bark surface among perithecia. Asci and ascospores were examined from perithecia on naturally infected stems. In the stands, C. parasitica was responsible for swollen or sunken cankers on stems. Water sprouts grew below the canker, and some of the twigs showed flag symptom. Abundant pycnidia and perithecia or the trace of them were found around some cankers.