The invention concerns a coaxial valve, particularly for the delivery of chemically aggressive fluids in the pharmaceutical and medical sectors and also for use in the food industry. The opening and closing of the valve is achieved in a combined pneumatic and magnetic actuating system, realised with the help of a pneumatic piston-actuator (13) and an obturator (14) positioned in parallel chambers, separated and constrained one to the other by means of permanent magnets (30,32) for the movements of the obturator in opposite opening and closing directions in response to the movements of the piston-actuator caused by a fluid under pressure.