Aluminum-doped zinc oxide nanoparticles were stably suspended in ethylene glycol (EG) without adding any stabilizing reagents. The Fourier transform infrared results showed that EG was chemically absorbed on the particle surface. The mechanism of particle stability of the suspension was proposed and analyzed. The operational pH (O.pH) and the zeta potential were observed to be dependent on the particle concentration. The O.pH increased linearly with the zeta potential as in aqueous suspensions and this relationship was independent of water concentration in EG. These empirical relationships are important in simplifying engineering approaches.