A suite of coals covering a range of properties was gasified in a pressurised thermogravimetric analyser (PTGA) at 950°C and 2.5 MPa. The reactivities of the coals to steam were measured to determine any relationships between coal properties and reactivity. Some of the coals were pre-pyrolysed to produce chars, and the reactivity of these chars was measured both in steam and CO2. The results show that no simple relationships exist but trends can be shown whereby reactivity increases with decreasing carbon content, increasing volatile matter and decreasing mean vitrinite reflectance. Coal minerals, notably CaO, also increased reactivity to some extent in coals of low carbon content, yet carbon content itself influenced reactivity more than mineral content. The effect of pre-pyrolysis of the coals on reactivity appears to be dependent on coal rank, with higher rank coals (carbon content above 83%) showing an increase in reactivity whereas lower rank coals show a marked decrease.