Introduction: Circulating nucleic acids can be obtained by minimally invasive procedures based on liquid biopsy, which has emerged as a promising area of investigation for screening and monitoring cancer treatment. Currently, tests based on circulating nucleic acid analysis, specifically cellfree DNA (cfDNA), are commercially available for diagnostic and prognostic investigation of a number of neoplasms. Objective: To describe the research on circulating nucleic acid markers for cancer prospecting in Brazil, since this area has advanced rapidly in recent years. Methods: In this systematic review, we surveyed Brazilian publications in cancer research focused on cfDNA and cfRNA present in different fluids. Both MEDLINE-PUBMED and EMBASE databases were inspected using terms such as "circulating nucleic acids", "cancer", and "Brazil". Results: The search returned 326 articles, in which 28 Brazilian translational studies were eligible. Different methodologies were reported for different types of cancer, in which cfDNA from plasma was the most investigated biological material. Molecular investigations included quantification, somatic mutation, RNA expression, genotyping, microsatellites, blood protein interaction, and methylation. Discrepancies in the regional distribution of the studies were also observed. Conclusion: Studies on circulating nucleic acid markers have advanced significantly in the oncology field, but many others are needed to better address the clinical practice in Brazil. [ABSTRACT FROM AUTHOR]