The Metrology Laboratories at Lockheed Missiles & Space Company (LMSC) are required to calibrate a variety of vacuum gages in support of research programs and manufacturing processes. Currently, primary standards for this purpose are obtained through calibration at the National Institute of Standards and Technology (NIST), which is a costly and time-consuming process. In an effort to reduce the reliance on external sources of calibration, this laboratory has developed an ultrahigh vacuum primary standard. A constant-volume, pressure drop flow meter designed at LMSC is used to generate a known flow rate of gas in a vacuum chamber partitioned by an orifice of calculated conductance. The pressure drop across the orifice at constant flow uniquely defines chamber pressure as a function of flow rate while in molecular flow. This constitutes a vacuum standard relying on dimensional, volumetric ratio, and differential pressure measurements only. The system was designed for use in realizing absolute pressures in the range from 10(-9) to 10(-3) Torr. Calculated pressures in the range from 10(-6) to 10(-3) Torr are compared to those measured by a NIST-calibrated spinning rotor gage. The overall viability of the system as an intrinsic standard is assessed and plans for future development towards that end discussed.