Fil: Sasbón, Jorge S. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado y Cuidados Intensivos; Argentina.Fil: Buamscha, Daniel. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado y Cuidados Intensivos; Argentina.Fil: Gianivelli, Silvina. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado y Cuidados Intensivos; Argentina.Fil: Imventarza, Oscar. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado; Argentina.Fil: Devictor, Denis. Hopital de Bicetre. Central Laboratory. Department de Pediatrie. Soins Intensift; Francia.Fil: Moreiro, Rita. Hospital de Pediatría Dr. Juan P. Garrahan. Departamento de Hepatología; Argentina.Fil: Cambaceres, Carlos. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado y Cuidados Intensivos; Argentina.Fil: Salip, Gonzalo. Hospital de Pediatría Dr. Juan P. Garrahan. Unidad de Trasplante de Hígado; Argentina.Fil: Ciocca, Mirta. Hospital de Pediatría Dr. Juan P. Garrahan. Laboratorio Nacional de Referencia para Hepatitis Virales: Argentina.Fil: Cuarterolo, Miriam. Hospital de Pediatría Dr. Juan P. Garrahan. Laboratorio Nacional de Referencia para Hepatitis Virales: Argentina.Fil: Vladimirsky, Sara. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Otegui, Lucio. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Castro, Raúl. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Brajterman, Leonardo. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Soto, Sonia. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: González, Jorge E. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Munné, María Silvina. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Objectives: To investigate the detection of hepatitis A virus ribonucleic acid in patients with acute liver failure and to assess if the results have any clinical implications for the evolution of acute liver failure in children. Hepatitis A infection, a vaccine-preventable disease, is an important cause of acute liver failure in children in Argentina. Universal vaccination in 1-yr-old children was implemented in June 2005. Design: Observational study in which patients were divided into Group 1 consisting of positive hepatitis A virus ribonucleic acid and Group 2 consisting of negative hepatitis A virus ribonucleic acid. Setting: Pediatric intensive care unit in National Pediatric Hospital "Dr. J. P. Garrahan," Buenos Aires, Argentina. Patients: Thirty-three patients with the diagnosis of acute liver failure secondary to hepatitis A virus infection and admitted to the Garrahan Pediatric Hospital between September 2003 and September 2005 were enrolled in the study. Twenty of these children were admitted to the pediatric intensive care unit. Interventions: None. Measurements and main results: Samples for total ribonucleic acid detection and genotyping were obtained from serum and/or stools on admission. We found positive hepatitis A virus ribonucleic acid in 13 patients and negative hepatitis A virus ribonucleic acid in 20 patients. The following clinical variables were evaluated: time of evolution, hospital stay, admission to the pediatric intensive care unit, pediatric intensive care unit stay, time on mechanical ventilation, criteria for orthotopic liver transplantation, and mortality. Characterization of the isolates did not reveal differences related to genotype; all cases were IA. No statistical significance was found as to the variables. However, positive hepatitis A virus ribonucleic acid showed lower percentages of pediatric intensive care unit admissions, criteria for orthotopic liver transplantation, number of orthotopic liver transplantation, and mortality than the group of patients with negative hepatitis A virus ribonucleic acid. Conclusions: Hepatitis A virus genotyping studies did not show any particularities, all cases were IA and, thus, apparent associations between genotype and the clinical presentation of acute liver failure could not be found.