Measured soot volume fraction profiles are combined with the modeled temperatures, velocities, and mixture fractions in an axisymmetric laminar diffusion flame to derive local soot formation rates. The flame is modeled by solving transport equations for momentum, mixture fraction, and enthalpy together with a radiation model. The measured soot concentration profiles are differentiated along the computed particle trajectories. The soot formation rates are correlated with local mixture fraction and temperature. Although the range of mixture fraction-temperature combinations available in this flame is not complete, the map provides quantitative information in the principal soot-producing region.