The prevalence rate of rotavirus in swine herds in Denmark was examined. 28 intensive breeding herds were tested and rotavirus was detected in 18 herds, i.e. 64.2%. Of the 638 fecal samples examined, 221 were positive (34.6%). The age distribution showed that rotavirus occurred with highest frequency (approx. 60%) in four week-old piglets. Rotavirus infection in neonatal piglets predominantly occurred in litters born by gilts. Production systems had influence on the occurrence of rotavirus. In traditional farrowing pens with loose sows, the prevalence rate was lower (28.3%) than in more restrictive farrowing pens with tethered sows and perforated flooring (43.3%). The most marked by difference occurred after the first two weeks when prevalence rate in piglets in restrictive farrowing pens rose distinctly over pigs in traditional pens (72.5% and 42.3%, respectively). The weaning age had distinct influence upon rotavirus shedding. Piglets weaned at two weeks had much higher prevalence rate (66.2%) than piglets weaned at 4-5 weeks of age (24.1%).