Diesel particles are formed and also reduced during diffusion-controlled spray combustion in the chamber of a Diesel engine. In earlier investigations it was found that the particles directly sampled near the exhaust valve were irregularly shaped, having a median diameter of 50 to 100 nm. The engine combustion process is cyclic and nonuniform and is imbedded in a highly nonstationary flow. The soot particles formed during the combustion process were emitted during the opening period of the exhaust valve together with the burned gas. This results in strong time-dependent fluctuations of the particle mass density in the exhaust pipe. It is the aim of this study to measure the dynamic particle behaviour during the exhaust gas flow. Laser light scattered by the diesel particles was measured very close to the exhaust valve. The light flux signals obtained under several fixed angles showed a periodic structure and were interpreted in terms of size parameters by applying the Mie theory.