In this letter, a generalized circuit model valid for the description of composite right/left handed metamaterial transmission lines with an arbitrary number of bands is presented for the first time. The model is a T- or π-circuit where the series branch is composed of parallel connected series resonators, and the shunt branch consists on series connected parallel resonant tanks. It is demonstrated that any arbitrary T- or π-circuit exhibiting alternate left-handed and right-handed bands can be expressed in the form of the proposed circuit. This justifies the consideration of the circuit as a generalized model of multiband metamaterial transmission lines. © 2008 IEEE.