Quantitative Laser-Induced Incandescence (LII) has been applied to investigate the soot formation in a combusting Diesel jet for various conditions.For the quantification of the LII signal the local soot volume fraction of a diffusion flame burner was measured using laser beam extinction. These data were used for the calibration of the LII signal.The investigation of the soot formation in a combusting Diesel jet was performed in a high pressure, high temperature combustion chamber with optical access. A wide range of pressure (up to 10 MPa) and temperature (up to 1,500 K) conditions could be covered using a hydrogen precombustion, which is initiated inside the chamber before fuel injection. The influence of different gas atmospheres have been investigated by varying the gas composition (H2, O2 and N2) inside the chamber.Local soot volume fractions (up to 12 × 10-6) of different combusting Diesel sprays were measured time (<100 ns) and 2D-spatially resolved (578 x 384 Pixel, <100 μm per pixel). The measurements indicate, that at the initial stage of combustion a decrease of the oxygen concentration of 25% (compared to air) reduces the maximum local soot volume fraction by a factor of 5 to 6. Additionally at this condition the ignition delay is longer.