A survey to detect antibodies against hepatitis E virus (HEV) was undertaken on 41 Spanish pig farms using an indirect enzyme-linked immunosorbent assay (ELISA). Forty of the farms (97.6%) were positive for anti-HEV IgG antibodies, while 34/41 (82.9%) had IgM positive animals. The highest proportion of IgG positive pigs comprised the adult sows (45/74, 60.8%; P=0.01), followed by young piglets aged 3-6 weeks (79/218, 36.2%). IgM positive pigs were more frequently found to be those animals > or = 12 weeks of age (P<0.001). In a second part of the study, the age distribution of the infection on one HEV infected farm was studied by combining the ELISA test with reverse transcription polymerase chain reaction (RT-PCR). On this farm, viraemia was mostly detected in animals aged 8-12 weeks and faecal shedding of HEV was detected in pigs of the same age. All HEV sequences corresponded to genotype 3. The study confirmed that HEV is spread in pigs in Spain and is probably endemic in many farms.