As part of a larger project comparing social and cultural features of violence in Japan and the United States, the threshold of violence was investigated by having respondents react to a series of scenarios in terms of what they or the police would or should do under the circumstances. The three scenarios involved a threat on the street, a threat at home by a drunken acquaintance, and a threat at home by a stranger. In both countries, a survey instrument was mailed to the sample, with a response rate of 30.3 percent in Japan and 29.4 percent in the United States. American respondents were twice as likely as Japanese respondents to say they would use a weapon when confronted by a stranger, by a known acquaintance, or if someone illegally entered their homes. The stated willingness to use a weapon was significantly related to whether one owned a weapon for personal safety and being male in both countries. Logistic regression showed the likelihood of responding to a threat by physical force to be twice as great in Japan and nearly eight times as great in Charlotte if the respondent owned a weapon. Data support the thesis of a weapons effect that influences one's definition of the situation. 15 references, 1 note, and 7 tables