Abstract: An eccentric rotary vane device useful either as an engine or a pump. The rotary device has a conventional main chamber, an inlet port and an outlet port communicating with the main chamber, a plurality of angularly related radial vanes, independently pivotable and rotatable about a vane axis within the main chamber. A rotor is eccentrically mounted with respect to the main chamber, and a power delivery shaft is connected with the rotor. Cylindrical vane guides in the form of a single roller or sets of two rollers engage the faces of adjacent vanes on either side so that the vane guides are maintained in substantially uniform engagement with the lateral faces of the vanes as they traverse radially inwardly and outwardly therealong during rotation of the rotor. The vanes have novel configurations on their lateral faces so that substantially a perfect seal is maintained between the vane guides and the lateral faces of the vanes when single rollers are employed as the vane guides and the number of vanes is odd.