Abstract: A modular oscillating piston-type fluid meter including a plurality of three or more oscillating piston measuring modules in stacked relationship to each other, each of the measuring modules having a piston operatively connected for synchronous, conjoint rotation with the pistons of adjacent measuring modules. The measuring modules are substantially identical to each other and include a body portion which defines a cylindrical chamber. Outlet and inlet ports communicate with the cylindrical chamber. Fluid is supplied to the ports by internal or external manifolding conduits.