A review of evidence on infant mortality derived from the London bills of mortality and parish registers indicates that there were major registration problems throughout the whole of the parish register period. One way of addressing these problems is to carry out reconstitution studies of individual London parishes, but there are a number of problems with reconstitution methodology, including the traffic in corpses between parishes both inside and outside of London and the negligence of clergymen in registering both baptisms and burials. In this paper the triangulation of sources has been employed to measure the adequacy of burial registration, including the comparison of data from bills of mortality, parish registers and probate returns, as well as the use of the same-name technique. This research indicates that between 20 and 40 per cent of burials went unregistered in London during the parish register period.