The recent progress of fuel cell development towards highly efficient and clean energy conversion allows increasing applications in the wide field of on-board electricity generation and alternative drive systems. Basic requirements and the status of proton exchange membrane (PEM) fuel cell development and its progress for hydrogen/air operation are analyzed. First car applications have demonstrated the high overall fuel efficiency and zero emission behavior of mobile fuel cell systems. However, the missing hydrogen infrastructure and the high volume necessary for hydrogen storage makes it desirable to have an on-board hydrogen conversion of liquid hydrocarbons available. Appropriate technical solutions in this field will have big markets in both mobile and stationary applications for decentralized power generation including a great impact on energy and environmental issues.