Abstract The post-ileal apparent digestibility (AD) of nutrients was determined, and a number of regression analyses of faecal AD of energy (E) and ileal AD of E and essential amino acids ( y) on cell wall constituents, faecal or ileal AD of dry matter (DM) and nitrogen (N) and faecal AD of amino acid ( x) were performed on data from a previous study. The post-ileal AD of nutrients for most feedstuffs and diets was positive, but very low. The mixed diets, which had the lowest average ileal AD of nutrients but the highest contents of cell wall constitutents and CP, had the highest average post-ileal AD of DM, organic matter (OM) and E, but were lowest in post-ileal AD of crude protein (CP) and amino acid (AA), especially lysine. There was little difference in the average post-ileal AD of nutrients or of cell wall constituents between cereals and cereal by-products and cornstarch-based diets. In general, the feedstuffs containing more E or OM and CP which had reached the large intestine had a higher post-ileal AD of E and OM, but a lower AD of CP and AA. It was concluded that the AD of nutrients cannot be predicted with sufficient accuracy by the contents of cell wall constitutents. However, the correlations between faecal or ileal AD of E and the faecal or ileal AD of DM were close, especially for single ingredients ( P < 0.001). Also, the correlations between ileal AD of essential AA (EAA) and ileal AD of N were close.