The paper charts the efforts to establish a successful niche position for the phosphoric acid fuel cell (PAFC) in stationary power generation, as a precursor to wider technological system and regime change. Market entry depends on matching price/performance characteristics to a niche, and improving performance through increasing returns, the most important and immediate of which are 'learning effects'. The paper identifies five types of learning effect: (i) migrating the technology to other niches and into the mainstream; (ii) opening the way for other technologies that may have greater scope for migration; (iii) transferring learning within the pioneering company to other technologies or products; (iv) transferring experience to others in the industry; and (v) enabling users to learn. Although PAFC may be perceived as a failure in some respects, a wider perspective suggests it has made a positive and useful contribution to learning.