In the 1980's, about 75 percent of firearms deaths in Canada were suicides, and almost 33 percent of all suicides involved firearms. To a large extent, therefore, preventing death by firearms means preventing firearms suicides. Opportunity theory underlying situational crime prevention suggests that gun availability affects the frequency of their use in suicide. The displacement hypothesis, however, predicts that reductions in the availability of one means of suicide will simply result in the displacement of suicidal intent to other means, with no overall suicide rate reduction. The displacement hypothesis was tested using Canadian data and two designs, regression analysis of regional variations in gun ownership and suicide rates and interrupted time series analysis of suicide rates before and after 1977 amendments to the Federal gun control law. This law introduced major new restrictions on gun purchase, ownership, storage, and use. The analyses found positive associations between gun availability and gun suicide rates and no evidence of displacement to other methods. 26 references, 4 tables, and 2 figures