A miniaturised hydrogen generator is being developed at the University of Newcastle for small mobile/onboard fuel cell applications. The Mark I version of the generator comprises several hundred micro-reactors each in the shape of a tubular vessel fitted with a multi-holed baffle-plate for mixing enhancement. Experiments were conducted on 1:1 scale replicas of the reactor over a range of temperatures between 300-1000oC using both partial oxidation (PO) and auto-thermal reforming (ATR) of methane. Results particularly at lower temperatures indicate that the application of ATR in conjunction with Ni-based catalysts leads to higher conversion rates of reactants and the higher selectivity of desired products (i.e. H2) when compared with those obtained from PO under Ni-base catalysts. However, the application of PO with Rhodium catalyst generates conversion rates greater than that of ATR with Ni-based catalysts.