Biodiesel has been increasingly used due to its property similarities with diesel and several other favorable characteristics with respect to exhaust emissions and biodegradation. For better understanding of biodiesel, this study examines the effects of the biodiesel blend fuel on VOC emissions from diesel engine exhausts in comparison with those from diesel fuel. Exhaust emission tests were performed several times for each fuel under the US transient cycle protocol from mileages of 0-80,000 km. VOC samples were collected from diluted exhaust by using thermal desorption tubes, then analyzed by a GC/MS system. Twenty-two and forty-seven chemicals are identified and quantified in B20 and diesel fuels respectively. Total VOC emissions are in the range of 32.4-71.6 mg kW h(-1) for B20 fuel, and 49.6-183.7 mg kW h(-1) for diesel fuel. Individual VOC emissions are in the ranges of 0.1-29.8 mg kW h(-1) for B20 fuel and 0.1-93.6 mg kW h(-1) for diesel fuel. Individual VOC health risks in terms of hazard quotients are in the ranges of 0.01-1.13, and 0.01-22.79 for B20 and diesel fuels, respectively. B20 has much lower total VOC emissions, decreasing by 61.2% on average; correspondingly, lower total ozone potentials of VOC reduce by 64.0%. The reductions in health risks are also shown in B20 fuel. As a result, use of biodiesel in diesel engines has beneficial effects in terms of VOC emissions. (C) 2011 Elsevier Ltd. All rights reserved.