Fundação Maria Emília de Carvalho Freire.Mutations of genotypic resistance to nucleotide analogues Entecavirand Tenofovirhave been described in patients undergoing treatment and virgins for hepatitis B virus. The present study demonstrated in a sample of 263 patients with chronic HBV from the North and Northeast of Brazil, a mutation rate of resistance to nucleotide analogues of 3.8% (10). Of the 10 patients who had genotypic resistance mutations, only 1 had no genotypic resistance mutation for the first line treatment for hepatitis B, entecavir and tenofovir.Due to the emergence of vaccine escape mutations and resistance mutations to antiviral treatment, and the severity of liver disease caused by HBV, screening for genetic mutations is important due to the impact on therapeutic management.