The design and integration of microfluidic devices for on-chip amplification of nucleic acids from various biological samples has undergone extensive development. The actual benefit to the biological community is far from clear, with a growing, but limited, number of application successes in terms of a full on-chip integrated analysis. Several advances have been made, particularly with the integration of amplification and detection, where amplification is most often the polymerase chain reaction. Full integration including sample preparation remains a major obstacle for achieving a quantitative analysis. We review the recently described devices incorporating in vitro gene amplification and compare devices relative to each other and in terms of fully achieving a miniaturised total analysis system (micro-TAS).