It depends on the poppy seeds. Evidently some poppy seeds are more potent than others, and eating just one or two rolls containing potent poppy seeds may result in a positive opiate test. But other rolls containing less potent poppy seeds may have no effect on a drug test. New confirmation procedures are being discussed that will be able to discern between drugs such as heroin and poppy seeds, therefore eliminating the possibility that poppy seeds could cause a positive test.