Immunofluorescent malarial antibody was measured in Nigerian children born in the UK, who had never been to any malarious country. Their antibody titres were compared to those of their mothers, taking into account the age of the children, the length of the mother's stay in the UK, and any revisits by the mothers to malarious areas. Antibody prevalence and titre fell with increasing age of the children. Their serum positivity rates were 82% in the first six months, 40% in the second six months and 9% at two years. Titres were generally low and declined similarly with age, from an initial geometric mean of 40 and 27 and 16, respectively, at the corresponding ages above. The clinical relevance of this finding to emigrant families returning home is briefly discussed.