Seroepidemiological evidence had suggested that pseudorabies (Aujeszky's disease) virus (PrV) infections occur in the European wild boar population in eastern Germany, although attempts to isolate the causative agent had failed. In 1995 and 1996, five virus isolates were recovered from latently infected wild boar originating from two regions where the disease was endemic. The isolates were identified as PrV by immunofluorescence and neutralisation with specific sera and grouped as PrV type I. Compared with reference strains and PrV isOlates obtained from domestic animals in the same region, considerable differences in the DNA patterns were detected. In particular, two additional larger BamHI-DNA fragments migrating in agarose gel electrophoresis between fragments 3 and 4 were observed, accompanied by the loss of fragments 5, 10 and 12. Southern blot hybridisation with fragment-specific DNA probes identified the larger fragments as fusions of BamHI-fragments 5 and 10, and 5 and 12, respectively, due to a loss of a BamHI-site in the inverted repeat regions. This distinctive fragment pattern has so far not been observed in PrV isolates from domestic pigs in Germany.