A preventive effect of restricted access to firearms on homicide rates was found in nine studies and on suicide rates in 19 studies. Methods were switched for homicide in one study and for suicide in 12 studies. Study findings on restricting access to lethal means for suicide other than firearms showed a preventive effect in 12 studies. Thus, restricting access to lethal methods for suicide appeared to have a preventive effect on suicide for both firearms and other methods. Further, method switching for suicide was more probable after limiting access to firearms than after limiting access to medications and gases. In general, research findings indicate that restricting the availability of a lethal method may reduce its use for suicide and homicide and that such restriction does not always lead to switching methods. More research is needed on who is likely to switch methods and under what conditions. Implications of the research findings for suicide and murder theories are examined, and the usefulness of the research in documenting the impact of restricting access to lethal implements in crime prevention is noted. 59 references, 5 notes, and 2 tables