The ISOFix system was developed to reduce the degree of misuse during the attachment of child restraints to vehicles, and to improve the dynamic performance of child restraints above that of systems attached by the adult belt. This paper discusses the issues involved and the practicalities of obtaining ECE R44 approval for an ISOFix system. Tests with ISOFix restraints designed for specific vehicles along with more general ISOFix restraints are reported. The results show that, where a car has been designed to work with an ISOFix restraint and the ISOFix restraint has been developed by testing in such cars, a two point ISOFix restraint can give equivalent performance to conventionally attached restraints. However, to be confident that an ISOFix CRS, that is assessed on a generic test, bench will perform well in any car with ISOFix anchorages, an additional feature that reduces the influence of the seat cushion could be necessary.