Necessary and sufficient conditions for azeotropy in reactive mixtures derived show that in the space of transformed compositions, they take the same functional form as the conditions for azeotropy in nonreactive mixtures. In general, reactive azeotropes do nor correspond to points of equal mole fraction (or mass fraction) across the coexisting equilibrium phases. The relationship between stationary points in the equilibrium temperature or pressure surface and reactive azeotropes is also considered, as well as their relevance to the Gibbs-Konovalov theorems.