Measurements of particle concentrations in one cylinder of a 1982 5.7 liter GM V-8 diesel engine have been made using a unique total cylinder sampling system. The first part of the paper is devoted to an examination of the performance of the sampling system. The role of blowoff and nucleation in the formation of sample artifacts is discussed.The remainder of the paper is devoted to the results of a study of the formation and removal of carbon particles during diesel engine combustion. Several operating conditions have been examined. The influence of injection timing, load, EGR, and oxygen addition on particle formation and removal has been investigated. The concentrations of volatile and nonvolatile particulate matter have been measured as a function of crankangle position. Particle formation begins 1-5 crankangle degrees (CAD) after the start of combustion. The particle concentration quickly rises, reaches a peak at about 10-20 CAD after the start of combustion, and then decreases toward the exhaust levels during the next 20-30 CAD. The peak concentrations are 5-15 times higher than the exhaust concentrations. Thus, particle oxidation during the expansion stroke plays an important role in determining exhaust emission levels.