The use of natural gas as a transportation fuel can offer: emissions and environmental benefits; energy diversity and security. Current reports suggest there are about 1,000,000 natural gas vehicles (NGV) operating around the world. One key component of NGV systems is the pressure regulator. Without accurate pressure regulation it is difficult, and costly, to obtain low emissions and good performance benefits from NGV.The paper discusses a precision, NGV, pressure regulator for fuel injection applications. Critical features of any regulator are flow and pressure* output (Pont) error. Pout errors include droop, creep and hysteresis. Fuel injector inlet pressures vary depending on the system design approach. Normally fuel injector inlet pressures vary between 1.7 to 17 bar. Additional topics of discussion include heat exchanger control, using manifold absolute pressure (MAP) to bias the regulator and the effects of undersized inlet and outlet fittings and hoses. Also supplied are comparative emissions test results for one- and two-stage regulators.The paper concludes that precision pressure regulation is a cost-effective method to obtain low emissions and good performance.