Abstract We constructed HindIII, SacI, and SmaI restriction DNA maps for hemorrhagic-pock monkeypox virus, Copenhagen strain (COPE); one hemorrhagic-pock progeny, CpCR virus, randomly selected from a COPE-infected CAM and twice pock purified; and two white-pock variants, CpCW-N1 and CpCW-N2 viruses, that were pock purified from separate CpCR-infected CAMS. Terminal region DNA restriction fragment molarity differences and DNA-DNA fragment cross-hybridizations between COPE and CpCR viruses suggested that a spontaneous transposition of DNA occurred during COPE replication on CAMS to produce CpCR virus. The maps of COPE and CpCR were identical except that the COPE 5 megadalton right-end inverted repeat region appeared enlarged in CpCR by the inverted insertion of a DNA segment of 8 megadaltons (Md) copied from DNA adjacent to the original 5-Md left-end repeat region. Thus, in CpCR each inverted terminal repeat region was 13 Md. Sequence differences between COPE and CpCR were apparent at the junction of the main genome body and the respective right-end repeat region of each. The DNA of COPE was determined to be 125 Md. The DNA of CpCR and CpCW-N1 viruses were each 133 Md and each had identical restriction maps with the enzymes above. Inspection of the map of CpCW-N2 DNA (119 Md) suggested that 14 Md of sequences adjacent to the CpCR right-end inverted terminal repeat had been deleted to produce this variant.