Grains of high-amylose maize starch (HAMS) were disintegrated (micronized) by jet milling with compressed air to alter their structure and properties. The disintegration resulted in decreasing the particle size in ay. from 14.62 mu m down to 6.14 mu m, in changing the particle shape to an irregular one and crystal structure to the B-type. After jet milling, the particle distribution curves become narrow and uniform but the grains lost their smoothness and become rough. Their crystallinity decreased from 34.63% down to 24.19%. The milling did not result however in formation of any new functional groups. The enthalpy of thermal transition decreased after the milling. All pasting temps. and sp. viscosities of micronized HAMS pastes also decreased but they showed a better viscosity stability and could be processed to the higher viscosity than the pastes of native HAMS.