The behaviour of a diesel spray, generated by a common-rail injection system, has been investigated. The experimental investigation was carried out by testing a high pressure injection system, for heavy duty direct injection marine diesel engines, to calibrate a reliable model for the simulation of liquid jet atomisation and droplet break-up of the fuel spray. The experimental facility comprised instantaneous measurements of the fuel injection rate and the characterisation of the spatial and temporal evolution of the diesel spray, injected in a high pressure, non-evaporative quiescent vessel. The fuel tip penetration was estimated by digital processing of spray images captured at different instants after the start of injection. The spray was modelled using KIVA-3v algorithm, with a Kelvin-Helmholtz, Rayleigh-Taylor spray break-up model on a 45 degrees sector grid. The mathematical model was verified with experimental results and a reasonable agreement was obtained.