Effects of a diet supplemented with caprylic and/or capric acid on piglet performance, apparent digestibility of nutrients, intestinal microflora and small intestine (ileum) structure were investigated. The experiment was performed on 252 piglets (24 litters) allocated to 4 experimental groups (6 litters each). The animals were fed with a standard feed mixture (control) or the same mixture supplemented with 2 g of caprylic or capric acid (groups C₈ and C₁₀, respectively) per 1 kg of feed. Group C₈+C₁₀ received 1 g of caprylic and 1 g of capric acid. Apparent digestibility was estimated using Cr₂O₃ as an indicator, while microbiological analyses were performed using standard agar plates. The short-chain fatty acid (SCFA) content of the ileum and caecum digesta was analysed using Varian 340 analyzer. The piglets receiving caprylic or capric acids grew significantly (P<0.01) faster than the control ones (average daily gains during the whole experiment, i.e. between days 1 and 84 of age, were: 288, 269, 278 and 234 g, respectively). The best feed utilization (1.3 kg per kg) was found in animals receiving caprylic acid. The acids also lowered piglet mortality, while significantly increased protein digestibility (P<0.01) and, to a lesser degree (P<0.05), also fibre digestibility. There was no significant difference in acidity of the digesta between control and experimental groups. Capric acid increased the amount of aerobic bacteria as compared to the control group, but the amount of Escherichia coli remained unchanged. The population of Clostridium perfringens was reduced by both caprylic and capric acids (P<0.01). Acids had no effect on SCFA content of the ileum but lowered the acetic acid content of the caecum digesta. Capric acid had the strongest effect on villi, which were significantly higher (306 μm) than in the control group (233 μm). Differences in crypt depth were smaller but the crypts were also the deepest in piglets receiving capric acid. The results suggest that caprylic and capric acids added to the feed improve piglet performance, probably due to positive changes in the mucosal epithelium structure of the ileum.