Introduced in this chapter is wireless middleware as a means of writing distributed applications for mobile environments. The concepts of middleware and the additional challenges that arise from wireless communications are introduced, in particular, low bandwidth and unreliability. Then described are the commercial wireless products currently available, with particular emphasis on the manner in which they solve challenges. The authors hope that greater appreciation of the capabilities of wireless middleware will enable future developers of applications for mobile environments to produce more efficient systems and researchers to produce better wireless middleware products.