Constructed wetland is a good example of environmentally friendly treatment system for water quality improvement.Current design model for constructed wetlands assume fnrst-order removal kinetics and plug-flow characteristics and is generally known as the k-C* model [1-3].The inadequacy of the model has been pointed out by various researchers [4,5].A kinetic model for horizontal subsurface-flow constructed wetlands used for phenol removal incorporating the dispersed hydraulic flow and the roles of both suspended and attached biomass in the degradation of the organics was developed.Two laboratory scale horizontal subsurface-flow constructed wetland units made of glass were set up.One unit was packed with graded gravel (2.4-4.8 mm) and the other with glass beads (16 mm) as the wetland media.