It is essential to reduce emissions from the existing vehicles, in order to preserve the environment. In this study, Karanja oil derived biodiesel generated particulates emanating from a medium-duty transportation diesel engine fitted with a diesel oxidation catalyst (DOC) were characterised. Regulated gaseous emissions, particle size-number distributions, elemental carbon (EC) and organic carbon (OC) of these particulates were determined under varying engine load conditions (no load, 25%, 50%, 75% and 100% load at rated torque speed of 2500 rpm) in order to assess the effectiveness of biodiesel blend (B20) compared to mineral diesel in combination with the use of DOC. Particle size-number distribution showed significantly higher concentration of nuclei mode particles for both test fuels. Particle size-number distribution was observed to be bimodal in nature and in two size ranges: less than 10 nm and 25-250 nm, respectively. This study reports few important insights into possible use of biodiesel in effectively reducing overall particulate emissions as well as gaseous emissions from automotive diesel engines fitted with DOC. (C) 2015 Elsevier Ltd. All rights reserved.