The Japanese public has been assumed to possess a deeply ingrained aversion toward the acquisition of nuclear weapons. We employ a survey experiment to ascertain whether this aversion is unconditional or may erode in the face of hypothetical deterioration in Japan's security situation, and in particular a hypothetical withdrawal of the US security-nuclear umbrella, increased North Korean nuclear weapons testing activities, and movement by South Korea toward the attainment of a nuclear arsenal. We find that the Japanese nuclear aversion may come under stress in the face of such developments. Additionally, we find that the elasticity of Japanese attitudes with respect to the nuclear option in the face of external security deterioration may be associated with an important individual-level demographic characteristic, namely, gender.