This study experimentally investigated the spark ignition characteristics of monodisperse bi-component (n-heptane, C-7/n-decane, C-10) sprays. Spray droplet diameters tested were 38, 44, and 49 mu m. Particular concerns were on the effects of species proportion and droplet size on the minimum ignition energy. The results indicate that minimum ignition energies increase with increasing droplet diameter for all the bicomponent fuels with different constituents, as for monocomponent fuels. The minimum ignition energies associated with 75%-C-7/25 degrees-C-10 bicomponent fuel sprays and pure C-7 sprays are nearly equal. Also, when the less volatile C-10 is the major species in the bicomponent fuels, the minimum ignition energies reduce considerably with the more volatile C-7 component increasing. It can therefore be inferred that mixing a certain amount of low-quality nonvolatile fuels into volatile fuels may not degrade the ignition characteristics of the fuel sprays, and blending a small amount of volatile fuels into low-quality nonvolatile fuels may significantly improve their ignition characteristics.