Pig studies on non-starch polysaccharides (NSPs) have mainly focused on finishing and breeding animals because their digestive capacity and ability to ferment fibre are considered greater than piglets. In this study, growth and nutrient digestibility, with particular reference to NSP constituent monomers, were evaluated in piglets offered contrasting sources of NSPs. The potential for enhancing growth performance and digestibility with exogenous food enzymes (xylanase, amylase, pectinase and beta-glucanase) was investigated. A total of 240 piglets weaned at 28 days of age, in groups of six, were allocated to six treatments in a 3×2 factorial design, diet type (W, B and SBP) by enzyme supplementation (–v. +). Diet W was wheat based and formulated to supply 14 MJ digestible energy (DE) per kg. In diets B and SBP, DE was reduced to 13·25 MJ/kg by replacing wheat with barley (708 g/kg) or with 185 g/kg dried unmolassed sugar beet pulp. Growth was monitored over 4 weeks. Digestibility of diets B–, B+, SBP– and SBP+ was evaluated in 16 piglets, in groups of four, using a 4×4 Latin-square design. In the growth study, mean initial and final piglet weights were 8·1 (s.e. 0·09) and 18·0 (s.e. 0·21) kg. Piglet health remained satisfactory and food intake averaged 523 (s.e. 6·7) g/day. There were no consistent and significant effects of diet type on food intake, live-weight gain or food conversion, except in week 1 when gain on diet W was higher than on diets B and SBP, 191 v. 150 v. 125 g/day, respectively (s.e.d. 20·0, P < 0·05). Enzyme supplements enhanced the conversion of food to gain over 4 weeks (1·56 v. 1·50:1, s.e.d. 0·030, P < 0·05). Piglets given diet SBP produced faeces with a lower dry-matter content (181 v. 246 g/kg, s.e.d. 10·8, P < 0·001) but with no visual evidence of a nutritionally induced diarrhoea. There were no significant differences in apparent faecal digestibility coefficients (AFDC) for dry matter, crude protein and gross energy between diets B and SBP. AFDC for soluble, insoluble and total NSP constituent monomers were higher (P < 0·001) in diet SBP. Soluble uronic acids were the most readily digested NSP constituents in diet SBP, showing a mean AFDC of 0·96 (s.e. 0·005). Apparent faecal digestibility was not an appropriate indicator for supplementary enzyme activity in the intact digestive tract of piglets given diets rich in fermentable NSPs. Piglets given the diets supplemented with enzymes excreted increased concentrations of urinary pentoses, especially arabinose (0·113 v. 0·136 mg/ml, s.e.d. 0·0107, P < 0·05). Urinary arabinose and xylose concentrations were also increased (V < 0·001) with feeding SBP, indicating that some of the microbially released NSP sugars escaped fermentation and were directly absorbed. In conclusion, piglets were able to use simple diets, containing high and contrasting sources of NSPs to support satisfactory rates of live-weight gain. Supplementation with NSP degrading enzymes enhanced the conversion of food to live-weight gain. Urinary NSP derived sugars provided indirect evidence of NSP hydrolysis by supplementary enzymes and gut microbes.