The dissemination of many antibiotic resistance genes has arisen among members of the family Enterobacteriaceae. The dissemination mechanism of these antibiotic resistance genes is closely linked with insertion sequence common region 1 (ISCRl). Thus, caution must be taken in clinical settings to prevent further dissemination of these antibiotic resistance genes. A nomenclature system of ISCRl variants, important for the antibiotic resistance dissemination, was proposed. The proposed system can designate all ISCRl variants on the basis of the detection time and by considering amino-acid substitution(s) compared with ISCRla. This nomenclature system of ISCRl variants can be applied to 19 groups (ISCRl to ISCR19) of the ISCR family and help some researchers to correctly designate new ISCR subgroups.