Thereislittle information concerning deciduous tootheruption pertaining tochildren oftheUnited KingdomandEurope.Therefore, dataonchildren fromthecurrent longitudinal growth study atthe ChildStudyCentre, London, wereexamined.For details ofthissample, methodofrecruitment, and investigations carried out,etc., reference may be made to Moore,Hindley and Falkner(1954). Briefly, thisunselected sampleofapproximately 200children consists ofthesame'healthy' children regularly andperiodically seenanddrawnfroman areainLondon. Thechildren areseenattheagesof4 weeks (± 2 days), 13,26,39weeks, 1year,18months (±7days), 2years andthereafter yearly (±14days). Thestate ofdentition isnotedateachvisit andfor thepurposeofthispaperthetotal numberof erupted teeth isgiven. Thedefinition oferuption usedisthatstagewhenpartofthecrownofthe toothhaspierced thegum(Robinow, Richards and Anderson, 1942;Doering andAllen, 1942; Falkner,