Differential scanning calorimetry (DSC) has been demonstrated to be a useful means of studying the reactivity of materials used in lithium-ion cells. In the present study, the reactivity of three most commonly used transition metal oxides, i.e. LixNiO2, LixCoO2, LixMn2O4, in the presence of electrolyte were investigated by DSC. The most commonly used negative electrode material, carbon (LixC6) was also studied. In the paper, relative levels of reactivity of the materials as a function of stoichiometry are reported. The implications of the results on the safety of lithium-ion cells are discussed.