Pea (Pisum sativum L) protein digestion in relation to particle size was studied in broilers. Birds were fed coarse pea (CP) or fine pea (FP) or nitrogen-free (NF) diets. Protein digestion was studied in gastro-intestinal contents of chicks by gel filtration and electrophoresis. Apparent ileal protein digestibility was lower for CP (70.2%) than FP (89.5%) diets. A decrease of protein digestibility appeared between ileum and excreta for FP diets. Endogenous proteins in ileal digesta represented important amounts. Estimation of excreta composition was about 24% of microflora in FP and CP. The molecular weight (MW) distribution of nitrogen compounds of diets were characterised by high proportions of components with, MW >15000. The relative amounts of very low MW (<500) components were in all cases lower for CP than for FP digesta. In intestine, proportions of high MW (>15000) components were higher for CP than for FP fed birds. Intestinal digesta of NF diet were characterised by higher MW than FP digesta. Similar electrophoresis patterns appeared for CP digesta and pea diet, whereas fine particles of CP and FP showed disappearance of protein bands. It is concluded that the CP diet leads to lower digestion of proteins than FP, but FP diets can lead to low MW proportion in intestine, which could be a limiting factor in pea protein digestion.