OBJECTIVE: To describe suicide rates by county size in the five geopolitical areas of Brazil. METHODS: This was an ecological, descriptive study of suicide deaths in Brazil that occurred among the population 10 years of age and older in 2004-2010. Data were obtained from the National Mortality Information System of Brazil. Counties were defined by size as: very large (200 000+), large (< 200 000-100 000), medium (< 100 000-50 000), small (< 50 000-20 000), very small (< 20 000-10 000, and micro (< 10 000). Age-adjusted suicide rates were calculated for all counties and for population-size groups in each geopolitical area. Rate ratio and 95% confidence interval were used to compare suicide risk between groups and the reference. RESULTS: The national, average suicide mortality rate was 5.7 deaths/100 000 inhabitants. Except in the North and North-East, suicide mortality rates increased from the very large (> 200 000) to the micro counties (< 10 000 population). Very high rates were scattered in the North and Mid-West among the indigenous peoples (> 30 deaths per 100 000). At highest risk were micro counties in the South (13.6 deaths per 100 000), with elderly males (60+ years, 31.4) and males 40-59 years (31.3) being the sex/age group with the highest rates. CONCLUSIONS: To reduce suicide mortality in Brazil, public health authorities must support mental health training in small cities and multi-professional interventions among the indigenous peoples. In addition, the causes behind underreporting of suicide deaths must be resolved in several areas.