Microreactor for carrying out methanol reforming for hydrogen production.The microreactor consists of a network of catalyst-packed parallel microchannels of cross-sectional dimensions from 400 to 1000 micrometers with a catalyst particle filter near the outlet fabricated by micromachining techniques, e.g., using photolithography and deep-reactive ion etching (DRIE) on a silicon substrate. Microchannel and filter capping, on-chip heating and temperature sensing, introduction and trapping of catalyst particles in the microchannels, flow distribution, microfluidic interfacing and thermal insulation are features of the microreactor.Another microreactor consists of a radial-flow configuration utilizing a annular shaped catalyst zone for carrying out reactions between gases introduced into the microreactor as the gases flow from an inner circular boundary to an outer circular boundary in a radial direction.Methanol to hydrogen molar conversion of at least 85% to 90% at flow rates enough to supply hydrogen to an 8 to 10 Watt fuel cell have been achieved.Microreactors according to the invention can be achieved to produce hydrogen as required for up to a 25 Watt fuel cell. Several such microreactors can be used simultaneously to generate hydrogen for fuel cells with higher power capacities.