Does gun ownership increase the likelihood that a person will commit a homicide? Findings from a recent case-control study (Kellermann et al. 1993) were interpreted as indicating that persons who lived in households with guns were 2.7 times as likely to become homicide victims as persons in households without guns. Problems with that study are identified, and a different approach is described. Survey data on a nationally representative sample of persons in prison for criminal homicide were compared with data on a nationally representative sample of the general population, in the first national case-control study of homicide. A logistic regression analysis was performed on the data, with the dependent variable measuring whether the subject was a killer, and the key independent variable being whether the person owned a gun. Control variables included age, sex, race, Hispanic ethnicity, income, education, marital status, region, veteran status, and whether the subject had children. Results indicated that gun ownership had a weak (odds ratio = 1.36) and unstable relationship with homicidal behavior, which was at least partly spurious. The promise and pitfalls of case-control research are discussed.