The quality of fuel injectors directly affects the performance of electronic fuel injection systems. They are traditionally evaluated by static flow, dynamic flow, linearity, repeatability, spray pattern and durability. The fuel spray pattern is usually examined only by observation. However, these parameters only indicate the macroscopic characteristics of injectors. These characteristics fail to depict the quality of fuel delivery, such as overall atomization, particle size distribution, and injector dynamic response. This paper presents an electro- optical system, a laser imaging system coupled with a particle analyzer, which magnifies and displays injector fuel spray in real time. The information is recorded on videotape and analyzed by a computer image analyzer.This equipment has been used to examine and analyze various current production and prototype fuel injectors. The quality of fuel sprays are analyzed in terms of particle size distribution at different locations of the stream, delay of fuel delivery, and shut-off. The irregularities such as drifting, dripping, and echo injection are also detected through the monitor display.It is believed that this technique is very useful for evaluating fuel injector microscopic qualities which are affecting engine system performance, fuel economy, and emissions.