High starch fractions (HSF) of navy, pinto and garbanzo beans were extruded with different moisture contents using a Wenger X-5 extruder. Increasing moisture content resulted in increased expansion index for navy and garbanzo beans and a decrease for pinto bean. The highest water absorption index was obtained for navy bean HSF at moisture 27%, for pinto 30% and for garbanzo 26%. For all beans, water solubility index decreased with increasing moisture. Color of extrudates also was affected by moisture. The extrusion process reduced trypsin inhibitor activity by about 70–85%, the level of decrease determined by moisture content of starting material and temperature. Extrusion temperatures of 121, 132 and 150°C inactivated hemagglutinating activity of navy, pinto and garbanzo beans.