This paper describes recent advances in passive direct methanol fuel cells (DMFCs) at the Korea Institute of Science and Technology (KIST). At KIST, we have been developing passive micro-DMFCs with capacities under 5 W that are expected to be used as portable power sources. Research activities are focused on development of membrane-electrode assemblies (MEAs) and design of monopolar stacks operating under passive and air-breathing conditions. The passive cells showed many unique features, much different from the active ones. Single cells with active area of 6 cm(2) showed a maximum power density of 40 mW/cm(2) at 4 M of methanol concentration at room temperature. A six-cell stack having a total active area of 27 cm(2) was constructed in a monopolar configuration and it produced a power output of 1000 mW (37 mW/cm(2)). Effects of experimental parameters on the performance were also examined to investigate the operation characteristics of single cells and monopoiar stacks. Application of micro-DMFCs as portable power sources were demonstrated using small toys and display panels powered by the passive monopolar stacks. (C) 2004 Elsevier B.V. All rights reserved.