The sex pheromone components for mating disruption of the rice leaf bug Trigonotylus caelestialium were examined in both the laboratory and the field. A rearing cage test in the laboratory showed that the copulation rate of T. caelestialium adults in cages treated with a dispenser loaded with the synthetic sex pheromone, a mixture of n-hexyl n-hexanoate, (E)-2-hexenyl n-hexanoate, and n-octyl n-butyrate (100 : 40 : 3), was lower than that of bugs in untreated cages, and that populations of the next generation were also reduced. In small-scale field tests (9 dispensers loaded with 50 mg of the sex pheromone placed at 5 m intervals in a 10 m×10 m square area), the numbers of males captured by traps baited with a lure containing the three components of the sex pheromone were reduced to some degree by treatment with either n-hexyl n-hexanoate or (E)-2-hexenyl n-hexanoate alone, or a 100 : 40 mixture of these two components. Furthermore, male capture by traps baited with the lure were mostly reduced by treatment of the 3-component sex pheromone, and also those baited with 3 virgin females. In large-scale field tests (200 dispensers each containing 300 mg of the 3-component sex pheromone in an area of 10,000 m²), the population densities of T. caelestialium and the numbers of males captured by traps in the treated fields were lower than those in the untreated fields.