Magnesium borate hydroxide (MgBO2(OH)) nanowhiskers with a diameter of 20-50 nm and a length of 0.5-3 mu m were synthesized via a facile hydrothermal route, using MgCl2-6H(2)O, H3BO3, and NaOH as the reactants. Mg7B4O13 center dot 7H(2)O with poor crystallinity was formed after coprecipitation of the reactant solutions at room temperature, the hydrothermal treatment of the slurry at 240 degrees C for 18h led to the formation of uniform (MgBO2(OH)) nanowhiskers with high crystallinity and preferential growth direction along the (200) plane.