As a proof of concept study, a micromachined polysilicon resistor was used as a vacuum pressure sensor. The resistor was healed to incandescence and operated with a constant electrical power input. A photodiode monitored light intensity changes as the pressure of the surrounding nitrogen gas was varied over the pressure range of 10(-2)-10(4) Pa. This optical method to measure pressure was nine times more sensitive than one based on electrical resistance variations. This measurement method is thus both more sensitive and it operates over a large pressure range than conventional thermal conductivity sensors.