This paper presents a design methodology and verification of a 2/5 GHz dual band digitally-controlled oscillator (DCO). The presented DCO employed two spiral inductors and a switching transistor between them to operate at two bands of frequency. The switch is controlled by a digital signal so that shifting from one band of frequency to another to control the operation of spiral inductors needs no analog voltage signal. The proposed circuit is implemented in 0.18 um CMOS technology and tested. The measured phase noise was -120.5 dBc/Hz and - 113.9 dBc/Hz (both @ 1 MHz offset) at carrier frequency of 2.7 GHz and 4.1 GHz, respectively.