The present invention provides microfluidic devices and methods using the same in various types of thermal cycling reactions. Certaom devices include a rotary microfluidic channel and a plurality of temperature regions at different locations along the rotary microfluidic channel at which temperature is regulated. Solution can be repeatedly passed through the temperature regions such that the solution is exposed to different temperatures. Other microfluidic devices include an array of reaction chambers formed by intersecting vertical and horizontal flow channels, with the ability to regulate temperature at the reaction chambers. The microfluidic devices can be used to conduct a number of different analyses, including various primer extension reactions and nucleic acid amplification reactions.