A laser 2-focus velocimeter (L2F) has been applied for measurements of velocity and size of droplets in the dense region of diesel spray. Investigated was the fuel spray injected intermittently into the atmosphere from an injector nozzle with the orifice diameter of 0.113 mm. The injection pressure was set at 40 MPa by using a common rail system. The L2F had a micro-scale measuring volume which consisted of two foci. The focal diameter was about 3 μm, and the distance between two foci was 17 μm. The maximum data sampling rate of the L2F system was markedly high as 15 MHz. Measurement was conducted at 25 mm downstream from the nozzle. The local mass flow rate and the number density were calculated at several specified times from the measured velocity, size, and arrival time of droplets. It was clearly shown that the mass flow rate was higher at the spray front than the inside, and was higher at the spray center than the periphery. The accumulated mass flow rate in the spray section measured by the L2F was almost equal to the amount of injected fuel mass within 5%. © 2011 The Japan Society of Mechanical Engineers.