An expanded food product was obtained from lentil flourcorn starchcorn oil mixtures by extrusion cooking. Effects of protein, lipid, and moisture contents of the feed mixture; cooking temperature and screw speed on starch gelatinization; protein insolubility; and lipid complexation were investigated. Effects of these functional properties on expansion ratio, cell size distribution, and cutting strength were assessed. Optimum feed composition was 67% lentil flour, 30% corn starch, and 3% corn oil (db). This mixture was processed at 15% moisture content and 178 degrees C temperature. Expansion ratio was 3.7 and degree of gelatinization was 0.70.