Wheat, corn and rice starch dispersions having water-starch ratios of 1.0:1.0, 1.5:1.0 and 2.0:1.0 (w/w) were heated in a microwave oven for 15 to 30 s and the degree of gelatinization was determined by differential scanning calorimetry. During 15 to 25 s of microwave heating, corn starch gelatinization rates were significantly lower and slower than wheat and rice starch rates. Beyond 25 s of heating no significant difference in the degree of gelatinization was detected. Microwave heating was nonuniform and produced chalky regions that were significantly less gelatinized than normally pasted regions. The chalky regions were due to the low water content. The quantitative quadratic model developed to depict the relation between water content and the rate of gelatinization during microwave heating of corn, rice and wheat starches showed a good fit with the experimental data.