A potato and wheat flour blend was processed in a twin-screw extruder at different moisture contents (16-21%) and screw speeds (200-400 rpm). The effect of these extrusion variables on the pasting behaviour of extruded products was studied, using a rapid visco analyser (RVA). The viscosity-related parameters determined include initial peak viscosity, cold paste viscosity and breakdown viscosity. Moisture content of the feed had a dominating effect compared to that of the screw speed of the extruder; an increase in moisture increased the aforesaid viscosity-related parameters. High moisture content of the blend changed the pasting characteristics of the extruded material to a great extent when the screw speed was between 200 and 300 rpm. The net specific mechanical energy was negatively related (p < or = to 0.05) to the viscosity-related parameters.