This paper presents a feasibility study of energy harvesting from ambient radio frequency (RF) sources. A preliminary assessment of the ambient RF energy was carried out by calculation of power spectrum density and measurement of received power in a common suburban area. The results showed that the median value of received power obtained -25dBm from 800 MHz band mobile telephone base station (BS) was averagely 13dB stronger than that from Digital TV broadcasting. A prototype multi-stage RF-DC conversion circuit was designed and tested. Experimental results showed that a 1.0 F electric double layer capacitor can be charged up to 320 mV in 3900 minutes at common suburban area. We confirm that the possibility of energy harvesting from ambient RF sources in suburban area, and clarify the problems in devices for the future energy harvesting systems.