This paper reports experimental measurements of film thickness for continuous fluid flow on the internal surface of a cone rotating about a vertical axis. Measurements were obtained via an optical method based on photographing the displacement of a grid projected onto the surface of the flow within the cone. Results are compared to analytical theory for axisymmetric, steady state, free-surface laminar flow of a Newtonian fluid in a spinning cone. The theory assumes that the flow is thin but takes account of gravity. The theoretical model is found to be in good agreement with the experimental results.