The collar rot disease has been reported recently and occurs at the 10-12-leaf stage of plants of opium poppy. Infected plants topple down and dry prematurely due to fast rotting at the collar region. The inoculum for this study was multiplied on the cornmeal-sand cuture. Genetic ratios were calculated by the ?2 test. Inheritance studies on this disease show a monogenic pattern of segregation with the ratio of 3 : 1 at F2, 1 : 2 : 1 at F3 and 1 : 1 at the backcross. Such genetic ratios clearly indicate that a single ressisive gene (rs-1) is responsible for disease resistance in opium poppy. The infrenece drawn on the basis of the present study will be a great help in the future breeding programme of opium poppy for collar rot resistance.