The key objective of this study is to evaluate and compare the main environmental life cycle impacts and energy balance of ethanol from sugarcane and biodiesel from soybean and palm oil, in the Brazilian conditions. The methodological tool used was the Life Cycle Assessment (LCA), in Well-To-Tank (WIT) perspective. A process based on cradle-to-gate attribution LCA method, was applied as the technique to assess the health and environmental impacts of ethanol and biodiesel production systems. The environmental assessment was carried out using the SimaPro 7.0.1 software and the CML 2 baseline 2000 methodology, developed by the Institute of Environmental Sciences (CML). The assumed common analysis base in this paper was 1.0 MJ of energy released by combustion of the analyzed biofuels. The environmental impacts were quantified and ranked in categories of impacts: Abiotic Depletion Potential (ADP), Global Warming Potential (GWP), Human Toxicity Potential (HTP), Acidification Potential (ACP) and Eutrophication Potential (ETP). In addition, the results were compared by meta-analysis with previous published studies. The Net Energy Relation (NER) in the life cycle of biofuels is an important indicator of the technical and environmental performance evaluation of biofuels production. In this study the NER of ethanol and biodiesel from soybean and palm oil were estimated and compared with previous published studies. Direct and embodied energy inputs, based on defined system boundaries, were used to estimate the energy requirement of crops production, juice/oil extraction, and ethanol/biodiesel industrial production. It is possible to conclude, that biofuel production systems with higher agricultural yields and extensive use of co-products in its life cycle present best environmental results. The analysis of obtained results shows that the choices of co-products allocation method, transport distance and inventory database of the country, have significant influence on the results of the life cycle environmental performance of biofuels. (C) 2014 Elsevier Ltd. All rights reserved.