The lethal exposure time to controlled atmospheres of high nitrogen at stored grain temperatures is an important information for control of stored-product insects. The mortality of 1-d-old egg, 1-wk-old (first or second instar) larva, 3-wk-old (fourth or fifth instar) larva, and 1-d-old pupa of Plodia interpunctella (Hübner) was determined at 18 ± 1, 23 ± 1, and 28 ± 1°C in 98% N₂ mixed with air. At 18°C, the lethal exposure times to achieve 100% mortality were 12.7 ± 0.7, 16.3 ± 0.3, 19.7 ± 0.7, and 14.7 ± 0.7 d for 1-d-old egg, 1-wk-old larva, 3-wk-old larva, and 1-d-old pupa, respectively. Temperature had significant effect on the lethal exposure time, and increase of the temperature significantly decreased the lethal exposure time. The order of the insect stages from the highest to lowest for LT₅₀ values was follows: 3-wk-old larva > 1-wk-old larva > 1-d-old pupa ≥ 1-d-old egg. The minimum lethal exposure times required to kill all stages of P. interpunctella were about 20, 16, and 12 d at 18, 23, and 28°C, respectively.