Waxy maize starch was extruded initially using a co-rotating twin-screw extruder. This extrudate was then equilibrated to either 18 or 23% moisture content, and subsequently re-extruded in a single-screw extruder at either 110 or 130 degrees C to characterize the melt viscosity. The melts exhibited shear thinning behaviour under all conditions; the power law index m increased with temperature, but did not significantly change with moisture content. Molecular weights of selected samples were measured by multi-angle laser light scattering (MALLS) in dimethyl sulfoxide/water (90/10 v/v). The initial extrusion pass reduced the molecular weight from 336 x 10(6) to 40 x 10(6). Molecular weight reductions during the second pass increased with increasing specific mechanical energy, and were less drastic than the initial drop. The observed M-W values display a semi-logarithmic dependence on the specific mechanical energy, with r(2) = 0.925. Specific mechanical energy can therefore be used to estimate molecular weight degradation, regardless of variations in extruder type or conditions during multiple passes. Molecular weight distributions determined using gel permeation chromatography correlated well with the single-point molecular weight determinations.