A pneumatic drive mechanism for use with positioning apparatus or the like, having a drive housing, a drive element such as diaphragm disk, piston or the like, movably seated therein and rigidly connected to a drive rod or similar device. The drive element is responsive to compressed air on one side thereof and to forces from at least one spring operating in opposed action to the compressed air. The spring is arranged within the drive housing. The drive mechanism also has a signal processing device such as a position controller, position encoder, limit signal generator, solenoid valve or i/p converter or similar devices. The signal processing device or devices are integrated within the drive housing in an accomodation space which is free of the spring or springs, of the drive rod and of the drive element.