The effects of diesel fuel properties and composition have been investigated in an advanced, low emissions, Detroit Diesel Corporation (DDC) Series 60 engine. The test results have revealed that particulates emissions in the U.S. transient test are governed mainly by fuel sulphur content and fuel density. The density effect is due to overfuelling of the engine which may result from how the cycle is calibrated and from how heavy-duty engines are governed under transitional operation. The model developed from these data correlates well with other published data and confirms the general case that fuel density, rather than aromatics content, is - with fuel sulphur - the dominant factor affecting exhaust particulates. The analysis of particulates composition supports these findings but reveals an additional fuel parameter, volatility, which has a minor second-order effect on particulates emissions.