Fluid transport is crucial in the development of microanalytical devices. While there are many micropump designs available, most are incapable of sustaining recirculation of fluid at muL/min to mL/min levels. We have designed and fabricated a positive displacement micropump by combining soft lithography with traditional bulk machining. The micropump is actuated through pneumatic pressure. The pump is self-priming and is suitable for recirculating fluid through a microfluidic device containing mammalian cell culture. By custom designing the volume of the pumping chamber, tight control of the output flow rate can be obtained by changing the actuation frequency. It can also be fabricated easily on plastic substrates without access to expensive microfabrication equipment. (C) 2004 Wiley Periodicals, Inc.