A combination of laser-induced incandescence (LII) and line-of-sight laser extinction were used to detect and quantify soot particles in and above ethylene-air flames produced by a laboratory flat-flame burner. The measurements include quantitative measurements of the spectrally and temporally resolved incandescence distribution of laser irradiated soot particles, images of the LII intensity distribution in the flame, and the effect of the laser irradiation on the total extinction of a weak probe beam. We have examined the onset of vaporization of the soot particles by the pulsed laser beam, and have determined particle temperatures and cooling rates from spectral analysis of the incandescence as a function of time after the laser pulse. LII imaging results are presented and a method for calibrating the images to yield spatial distributions of soot volume fraction is demonstrated. The measurement results illustrate the potential of LII for quantitative soot detection in combustion systems, in both the flame zone and the exhaust stream.