The moisture content of iron ore is important in handling, stockpiling, transport and further processing operations. Typically these ores contain both `free' and `bound' moisture, the latter being moisture that is not removed in a conventional laboratory determination of moisture by air drying at 105C, and it is the free moisture that is important in dust control and ore handling. The CSIRO Division of Mineral and Process Engineering has previously developed and commercialised gauges, based on capacitance and microwave techniques, for the on-belt determination of moisture in coal and minerals. However, these gauges determine total moisture, and have a different sensitivity to free and bound moisture in the material analysed. Consequently, the accuracy of determining total or free moisture alone may be significantly affected by variations in the bound moisture content. An investigation has been carried out on the simultaneous determination of free and bound moisture in iron ore fines (< 6 mm) by microwave techniques. The results of this investigation have demonstrated that both free and bound moisture are most accurately determined from a combined measurement of microwave attenuation and phase shift, in the frequency range of 2.6 - 4 GHz. Using this technique, free moisture has been determined to 0.34 wt% over the range 0 - 7 wt%, and the bound moisture to within 0.70 wt% over the range 3.5 - 7.9 wt%.