We performed a retrospective study to determine the age- and sex-related normal values of absolute 99Tcm-DMSA uptake at 24 h in children with normal kidneys. Of the 576 scintigrams performed between 1993 and 1996, 136 (272 kidneys) were classified as 'normal' by two independent observers on the basis of the presence of a smooth cortical outline, the absence of cortical loss, relative uptake in the range 45-55% and normal echographic parenchymal findings. The 136 scintigrams were divided into eight groups based on the children's age: Group I, < 1 month (2 boys); Group II, 1-3 months (6 boys, 8 girls); Group III, 4-7 months (7 boys, 6 girls); Group IV, 8-12 months (8 boys, 8 girls); Group V, 13-24 months (14 boys, 4 girls); Group VI, 25-36 months (6 boys, 13 girls); Group VII, 37-120 months (13 boys, 19 girls); Group VIII, 121-180 months (8 boys, 10 girls). In contrast to the results of Morris et al. using absolute 99Tcm-DMSA uptake at 4-6 h, we found that combined left and right kidney uptake increased until age 8 months (Group I, 22.0 +/- 6.7%; Group II, 45.9 +/- 5.0%; Group III, 50.8 +/- 5.0%; Group IV, 56.9 +/- 8.5%; P = 0.019), after which it reached a plateau (Group V, 55.4 +/- 7.3%; Group VI, 60.1 +/- 7.8%; Group VII, 62.0 +/- 5.0%; Group VIII, 62.4 +/- 6.3%). Uptake at 24 h tended to be lower in the girls than in the boys, but this difference was not significant.