Seedling rot occurred on burley tobacco at the early growing stage after transplanting was surveyed in the Chonbuk province, the main area for burley tobacco production, during the 3 crop years from 1986. The incidence of disease was about 0.6-0.7% every year and major causal organisms were Pythium spp. More diseased plants were observed in the fields in which tobacco planted with improved mulching system than in that with any other mulching system. The temperature and relative humidity in the planting hole covered with polyethylene film for 11 days after transplanting were recorded by 27-45$^{circ}C$ and 75~95%, respectively. The punched polyethylene film mulching field showed less diseased plants than that with improved mucking. In improved mulching system the longer period of mulching caused higher incidence of seedling rot(r=0.74**). Soil drench treatment of 200m1 of aqueous Metalaxyl Solution(125ppm) was effective to control the disease.