Due to their low specific speed, Periphery pumps, allow high heads with small flow rates and present performance curves with very stable features. This kind of pump is also smaller and simpler to construct than equivalent volumetric pumps though they have a fairly low efficiency, due to the inherent characteristics of their fluid-dynamic behaviour.Over the past few years, periphery pumps have been subject to more and more interest in the automotive field, as injection pumps in spark ignition engines, in fact, for this purpose, they are highly competitive due to their reduced dimensions, low cost, high reliability and good priming behaviour.In the past many theories were presented to explain the behaviour of periphery pumps and to calculate their performances, but these theories usually need extensive experimental support. Hence, it is very interesting, from an industrial point of view, to find efficient theoretical means which are able to forecast the periphery pump performances, using easy to find geometric and fluid dynamic parameters.A hypothesis for the evaluation of the circulatory flow rate is put forward in this paper; this theory is based on the consideration of the centrifugal force field in the side-channel and in the impeller vane grooves. For the determination of head-flow rate curves, a traditional momentum exchange theory is used and a comparison between theoretical and experimental data is presented.Two innovative periphery pump constructive solutions have also been designed, built and experimentally tested. The first is a double stage periphery pump where the two stages have been constructed on the same impeller while the second has a particular technical solution which presents some interesting features for the design of the motor-impeller group.