OBJECTIVES: This study examined errors in estimating household gun ownership that result from interviewing only 1 adult per household. METHODS: Data from 2 recent telephone surveys and a series of in-person surveys were used to compare reports of household gun ownership by husbands and wives. RESULTS: In the telephone surveys, the rate of household gun ownership reported by husbands exceeded wives’ reports by an average of 12 percentage points; husbands’ reports also implied 43.3 million more guns. The median “gender gap” in recent in-person surveys is 7 percentage points. CONCLUSIONS: Future research should focus on respondents’ reports about personally owned guns.