(Archer et al., 1965). By comparison our figure of 37% is surprisingly high, and as examination of a single specimen must be regarded only as putting a lower limit on the number infested, a more thorough search would doubtless have yielded more positives.The various regions covered by our survey contributed roughly equal numbers of boys and girls with the single exception of Pakistan, where boys outnumbered girls by five to one. This exception presumably has a sociological basis which may extend to the finding of a greater hookworm carriage rate in boys, whereas the girls of this population have higher carriage rates for both hymenolepis and ascaris. The Pakistani girls and boys thus behave as distinct populations; perhaps the activities of the boys make them more liable to acquire hookworm and the activities of the girls make them prone to acquire hymenolepis and ascaris. We have not determined the reason for these differences.The regional differences in the carriage patterns have already been considered but the low carriage rate in the African group (Kenya 16% and Uganda 7%) contrasts with the high rate in the West Indian group (51%I) and South-east Asian groups (30-40%). The dominance of trichuris infestations and the absence of hymenolepis are notable in those from Hong Kong and the West Indies.Our figures clearly indicate the need to examine the faeces of all newly arrived immigrant children, using a concentration method when possible. While many infestations are probably light and will disappear in time, they nevertheless require recognition because the carrier may suffer disease. The possibility of medical and surgical manifestations of infestation must be constantly in mind when dealing with these children. Secondly, as has been pointed out by Buckley and Pester (1965) and by Archer et al. (1965), there is a risk of transmission of helminths in this country, and the large number of children infested constitute a substantial reservoir. These authors give five instances where transmission has taken place to children who have never been abroad-three cases of hookworm, one case of hymenolepis, and one case of ascaris-and it must be assumed that other unrecognized instances exist.The risks of transmission are largely unknown and depend on variable climatic conditions as well as on social circumstance. The hookworm requires warm, humid conditions-a hot wet summer-to develop in earth to the larval infective stage which then penetrates the skin. Eggs of ascaris and trichuris require only a period for embryonation before becoming infective.Hymenolepis ova require only transmission to the mouth for infection. In a recent study in Prague (Kawaciukova, 1971) eggs of Enterobius vermicularis were found in modern heated swimming pools; the author also stated that the ova of ascaris, trichuris, and hookworm will mature despite a chlorination level of 0-2-0-3 mg/litre-that is, 0-2-0-3 p.p.m.-residual chlorine, which is adequate for bacteriological purposes. We have incidentally observed that these eggs will continue to ...