Amorphous MoO2(+delta)(delta approximate to 0.3) has been synthesized at ambient temperatures by a reduction of aqueous potassium molybdate solution with potassium borohydride. The sample has been characterized by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The amorphous MoO2+delta exhibits excellent cyclability with a capacity of over 200 mAh/g in the range 3 to 1 V in lithium cells. The electrochemical behavior of amorphous MoO2+delta is distinctly different from that of crystalline MoO2. Good cyclability at low enough voltage range makes amorphous MoO2+delta an attractive candidate for anode hosts in rocking-chair lithium cells.