A study is made of the kinetics by which particles in a high-temperature aerosol coagulate. The experimental method uses a light-scattering technique coupled to a shock tube, and allows a continuous record to be made of the changes in particle volume during the coagulation process. The theory of free-molecule coagulation of aerosols with a self-preserving size distribution has been developed to include the effects of dispersion forces and a comparison made between theoretical and observed rates of coagulation of a molten lead aerosol at temperatures around 940 K. Observed rates are found to be a factor of two faster than theory would predict.