<div class="htmlview paragraph">A new real-time soot concentration measurement technique for engine exhaust flows is presented. The technique uses a pulsed laser to illuminate the soot particles, with subsequent detection of the incandescence from the particles. Results are presented which show the detection limit, dynamic range, and dependence on operating conditions (i.e. size distribution and particle composition). The main advantages of the technique are its ability to detect small concentrations of soot such as those which would be present in the new clean diesel engines, its ability to give time-resolved measurements during the exhaust stroke, and its relative insensitivity to variable operating conditions.</div>