a device for the treatment of erectile dysfunction or for penile exercise includes a vessel defining an elongated vacuum chamber and a mouth opening leading into the vacuum chamber . an annular pumping sleeve is mounted on , and slidingly displaceable relative to the vessel . the device includes valving arranged such that reciprocation of the sleeve relative to the vessel serves to pump air out of the vacuum chamber . the device further includes a constriction ring which is sealingly and dismountably mountable on the vessel , and which is configured sealingly to engage with an outer surface of a human penis inserted into the vacuum chamber .