Abstract: An ambulatory pump (10) for dispensing a liquid under pressure at a predetermined flow rate includes a housing (12) having first and second end caps (14, 16) positioned on the housing (12) and enclosing the housing (12). Each end cap (14,16) has a port (18,20) formed therein. A pressurizable bladder (22) is carried by the housing (12) for receiving and dispensing the liquid. The bladder (22) is expandable between an unexpanded condition and an expanded condition. The bladder (22) has a free end (30) defining an opening in flow communication with the second end cap port (20) and a fixed end defining an opening in flow communication with the first end cap port (18). A section of flexible tubing (40) is carried by the housing (12) and extends between and is in flow communication with the bladder free end (30) opening and the second end cap port (20).