The aim of the present study was to detect acute Hepatitis E virus (HEV) infection in patients with abnormal alanine transaminase (ALT) in which other viral hepatitis infections had been excluded in southern Spain, an area adjacent to regions where this disease is endemic. Of 336 sera tested 30 (8.92%) were positive for IgM antibodies against HEV (anti-HEV IgM) and 7 (2.08%) were negative in a repeated assay. Immunoblot analysis (IBA) was applied to the 37 positive sera in the first assay; its results were positivity for 26 (7.73%), ambiguous for 5 and negative for 6 sera. Amplification of ORF1 and ORF2 of HEV by means of nested RT-PCR was carried out with the 37 sera that were either positive or ambiguous by ELISA; a positive result was obtained only with one serum for the ORF2 protein. IgM antibodies against the HEV ORF2 protein could be a useful marker in the diagnosis of acute infection and a substitute for the determination of viral RNA in serum; this is of both diagnostic and epidemiological importance as it would allow the patients transmitting the infection to be recognized by means of a simple determination of antibodies. The sequence of the ORF2 fragment of HEV occurring in samples taken from both humans and animals amplified in this study has considerable homology with the sequences of HEV strains/isolates of European origin. These results demonstrate that an autochthonous HEV circulates in Spain.