The Asiatic rice borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), is an important rice pest in East and Southeast Asia regions. We developed a simple technique for determining the mating status of C. suppressalis males. This technique involves examining the white secretion in the last segment of the primary simplex of the C. suppressalis male. The technique is easily used in either the field or the laboratory to confirm mating status. Examination of pheromone-trap-captured males showed that most were mated (∼85%). This high percentage of mated males indicates that proper pheromone density is necessary for the effective use of pheromone traps in C. suppressalis management.