Two distinct heavy fuel oil (HFO) sprays were generated by a twin-fluid atomiser, for differing atomising air to fuel ratios and investigated under non-reacting conditions in a spray test rig in which their radial mass distribution and mean droplet size and distribution were determined. Both sprays exhibit solid cone type distributions in their atomisation pattern—with that of the lower atomising air to fuel ratio having a more sharply defined central peak. Increasing the atomising air to fuel ratio reduces the droplet size distribution, producing a spray with a greater uniformity in its radial variation. The sprays, however,subtend approximately the same angle. The atornisation tests were followed by combustion measurements in a large-scale laboratory cylindrical furnace for both sprays. Measurements of mean gas temperature, species concentrations (02, CO2, CO and unburnt hydrocarbons) and incident wall radiation nux are reported. The two flames exhibit distinct vapourisation rate histories which may be attributed to differences in droplet size and spray momentum. The data presented are intended to provide a better understanding of the relationship between spray quality and combustion performance and to assist the validation of mathematical models for prediction of HFO combustion.