  We analyze dephasing in single and double quantum dot systems. The
decoherence is introduced by the B\"{u}ttiker model with current conserving
fictitious voltage leads connected to the dots. By using the non-equilibrium
Green function method, we investigate the dephasing effect on the tunneling
current. It is shown that a finite dephasing rate leads to observable effects.
The result can be used to measure dephasing rates in quantum dots.
