Selected measurements of the in-cylinder soot loading and the gaseous combustion products for ten different innovative fuels, burned in a D.I. diesel engine are presented and discussed. All the fuels which were tested have a very low sulfur content, so the insoluble fraction of the particulate is mainly composed of soot. Two different measure techniques are applied: the two-color pyrometry optical method and the fast sampling of gaseous products in the combustion chamber. A priori and experimental uncertainties relative to the reduction of the data obtained with the two-color measurements are preliminarily investigated. The main results which were obtained are: a) in pure paraffin fuels the measured soot loading strongly depends upon the cetane number; b) only in lower (< 58) cetane number fuels the soot loading depends on the aromatic fuel content; c) tests performed with the fast sampling technique confirm the main trends found when performing measurements with the two-color technique.