BACKGROUND: Between 1950 and 1995 suicide rates in Sri Lanka increased 8-fold to a peak of 47 per 100,000 in 1995. By 2005, rates had halved. We investigated whether Sri Lanka's regulatory controls on the import and sale of pesticides that are particularly toxic to humans were responsible for these changes in the incidence of suicide. METHODS: Ecological analysis using graphical and descriptive approaches to identify time trends in suicide and risk factors for suicide in Sri Lanka, 1975-2005. RESULTS: Restrictions on the import and sales of WHO Class I toxicity pesticides in 1995 and endosulfan in 1998, coincided with reductions in suicide in both men and women of all ages. 19,769 fewer suicides occurred in 1996-2005 as compared with 1986-95. Secular trends in unemployment, alcohol misuse, divorce, pesticide use and the years associated with Sri Lanka's Civil war did not appear to be associated with these declines. CONCLUSION: These data indicate that in countries where pesticides are commonly used in acts of self-poisoning, import controls on the most toxic pesticides may have a favourable impact on suicide. In Asia, there are an estimated 300,000 deaths from pesticide self-poisoning annually. National and international policies restricting the sale of pesticides that are most toxic to humans may have a major impact on suicides in the region.