Abstract: An elastomeric infusion pump apparatus includes an elastomeric bladder and an axially-variable core positioned within the bladder. The bladder and the core are co-operable between a first state in which the bladder has expanded the core and a second state in which the core stretches the bladder. An apparatus for infusing a pharmaceutically active liquid supplied by an external source includes an elastomeric bladder and an axially-variable core positioned within the bladder. The bladder and the core are co-operable through an infusion cycle during which the bladder axially expands the core as the liquid is forced into the bladder from the external source, the bladder forces the liquid through the core after the liquid has been forced into the bladder, and the core radially stretches the bladder after the bladder has forced the liquid through the core.