IC Engines are widely used as power plants for automobiles. The rapid growth in the number of automobiles has caused increased environmental pollution. Therefore, emission legislation was introduced to keep the pollution within acceptable limits. It is becoming more stringent day by day, and is the driving force for the development and application of various experimental and computational techniques for engine combustion and emission studies. Multi-stage fuel injection, VCO nozzles, retarded fuel injection timing, reentrant combustion chamber, etc. are some of the means of reducing the exhaust emissions. A study involving in-cylinder combustion visualisation and an optical method (spectroscopic method) is reported in this paper. Using this technique, the effect of multi-stage fuel injection at various engine operating conditions was studied.A Ricardo Hydra single cylinder, direct injection optical diesel engine was used for this study. This engine has an optical window in the piston that enabled the in-cylinder flow and combustion to be visualised. A high-speed cine camera and a powerful pulsed laser were used to obtain the combustion photographs. Later these photographs were processed using the optical technique (spectroscopic method) and image processing, and quantitative information was obtained viz. the flame temperature and soot concentration. Also using this technique, the effectiveness of multistage fuel injection was studied. The information, thus obtained, was correlated with the exhaust smoke. It was useful for better understanding of the in-cylinder phenomena. In spite of some limitations, this technique demonstrated its ability as a potential tool for engine combustion and emission studies.