As part of a more comprehensive study, complete residential histories were collected from 109 cases of childhood leukaemia and non-Hodgkin's lymphoma who were diagnosed while resident in Gateshead, West Cumbria or North Humberside (1973-1987), and who were born in the same areas. Corresponding data were obtained from the same number of controls matched by date of birth, sex and area of residence at diagnosis and birth. Altogether, 1332 years of residential history were available for analysis and of these 131 (9.8 per cent) included a change of home. Moving house was much more frequent for both cases and controls in the first two years of life (69 out of 432 child-years, i.e. 16 per cent). The moves were mostly over short distances, with only 23 per cent being 5 km or more and only 9 per cent into another administrative district. Twenty-eight per cent of the children had moved house at least once by their second birthday and 48 per cent by the age of five years. Few case-control differences were apparent and none achieved statistical significance. There was a suggestion of more mobility for case children in the first few years of life, especially for cases diagnosed shortly after the removal. When the residence of mothers in the year preceding the childrens' birth was examined, there were relatively few removals in this period (26, i.e. 24 per cent, altogether, of which 14 were over 5 km and nine from another administrative district). Of these, 18 case mothers had moved (11 over 5 km) compared with eight control mothers (three over 5 km).(ABSTRACT TRUNCATED AT 250 WORDS)