In recent years, use of the venturi for measurement of gas-particle flows has received considerable attention. The technology for the venturi as a single-phase flowmeter has matured to the point that application is routine. Much more research, however, is required to establish the venturi as an acceptable gas-particle flowmeter. The first part of this paper consists of a discussion of the basic principles of venturi pressure-flow performance for gas-particle flows. This is followed by a description of the experimental calibration of a venturi for measurement of gas-particle flows with particle-to-gas mass-loading ratios up to 35. Next, a modified Stokes number is presented and shown to improve correlation of venturi pressure-flow data. Finally, the predictions of a model presented by Doss are compared with the pressure-flow data of the venturi calibration performed in this work. The Doss model provides good predictions of venturi differential pressures for particle-to-gas mass-loading ratios less than ten but tends to overpredict the differential pressure, by as much as 45 percent, for particle-to-gas mass-loading ratios above 10.