Two experiments were conducted to investigate the effect of expander processing of food for growing and finishing pigs. Experiment 1 examined the effects of expander processing on the nutritive value of a cereal-based diet and a pea-based diet for pigs while experiment 2 determined the effects of extrusion and expansion of the peas component of the diet on the nutritive value. In experiment 1, growth performance, carcass characteristics (no. = 12) and nutrient digestibility (no. = 4) were determined in pigs offered individually food containing a cereal diet (T1), a complete cereal diet that had been expander processed (T2), a 400 g/kg peas diet (T3) or a complete 400 g/kg peas diet that had been expander processed (T4). The expanded diets were processed at 105°C for 5 s at 35 bar pressure. In experiment 2, productive performance and nutrient digestibility were determined in pigs (no. = 12) offered individually diets including a control cereal diet (no peas) (TT1), a 400 g/kg raw peas diet (TT2), a 400 g/kg expander processed peas diet (TT3) or a 400 g/kg extruded peas diet (TT4). The pea portions of the diets were extruded at 130°C for 30 s and expanded at 130°C for 10 s at 42 bar pressure. In experiment 1, the inclusion of peas in the diet reduced (P < 0·001) the digestibility of the organic matter (OM) (0·871 v. 0·893, s.e. 0·003), protein (0·867 v. 0·907, s.e. 0·004) and energy (0·857 v. 0·880, s.e. 0·003). Expansion had no effect on the nutrient digestibility of the diets, however, it did increase (P < 0·05) the digestible energy content of the cereal diet. The inclusion of peas in the diet reduced (P < 0·05) daily gain (0·929 v. 0·999, s.e. 0·024 kg/day) and increased (P < 0·001) food conversion ratio (FCR) (2·31 v. 2·16, s.e. 0·029) from 34 kg to slaughter. Expansion had no effect on daily gain or FCR. In experiment 2, OM digestibilities of 0·891, 0·872, 0·882 and 0·885 (s.e. 0·0042) (P < 0·01), protein digestibilities of 0·905, 0·879, 0·874 and 0·877 (s.e. 0·0069) (P < 0·001) and gross energy digestibilities of 0·875, 0·861, 0·870 and 0·875 (s.e. 0·005) (P < 0·05) were recorded for TT1 to TT4 respectively. Gains (kg/day) of 0·981, 0·927, 0·940, and 1·016 (s.e. 0·036) (P < 0·05) and FCR of 2·17, 2·32, 2·28 and 2·18 (s.e. 0·037) (P < 0·05) were recorded for TT1 to TT4 respectively. In conclusion, expansion had no effect on the nutritive value of food for pigs.