This review highlights the recent progress in synthesizing some representative metal-oxide nanocrystals (MONCs) with controlled magnetic, electronic, and optical properties for potentially important technological applications. It first introduces the synthesis of MONCs of magnetite (Fe3O4), ferrite (MFe2O4), and hollow Fe3O4 with controlled magnetic properties. It then highlights the potentials of these nanocrystals (NCs) as highly effective contrast enhancement agents for magnetic resonance imaging (MRI) and as efficient nanoplatforms for target specific drug delivery. The review further surveys some typical high-temperature solution-phase approaches to the common semiconductive MONCs of indium tin oxide (ITO, In2O3·xSnO2)/tin oxide (SnO2), zinc oxide (ZnO), titanium oxide (TiO2), and copper oxide (Cu2O or CuO) with controlled band-gap energies and optical properties for optoelectronics, photocatalysis, and sensor applications.