Constructed wetland systems for the treatment of wastewaters, pollution control and environmental enhancement have been gaining increasing international interest and application. This interest has was stimulated by the 1986 Piracicaba Conference at which the IAWPRC Specialist Group was motivated, followed by specialist conferences in Chattanooga 1988, Cambridge 1990, Sydney 1992, and subsequently the present conference in Guangzhou 1994. During this time it is estimated that over 1000 wetland systems have been implemented as well as many research projects throughout the world into the mechanisms and performance optimization of such systems for a wide variety of applications and objectives. This paper provides a brief review of some of the existing understanding of the technology, identifying recent design philosophies, performance expectations and some limitations to present understanding and confident design basis.