Sheep pox virus DNAs from field isolates and vaccine strains were analysed by digestion with the restriction enzymes PstI and Bam HI. The restriction profiles generated by these enzymes show very close relationship between isolates from different geographical regions. The patterns of isolates can be grouped by the animal of origin (e.g. a cattle pox isolate can be differentiated from sheep pox isolate). The molecular weights of the genomes of different isolates varied from 91 to 94 MDa. The restriction enzyme patterns can be used as a molecular epidemiological tool for differentiating field and vaccine isolates.