The evaluation of delayed cutaneous hypersensitivity by using a standardized test system offers an assessment of cell-mediated immunity. The number and diameter of positive responses induced by seven antigens result in a score. The study included 21 healthy children, 20 children with bacterial infections as well as 20 patients with chronic renal insufficiency. In addition, 16 children with cystic fibrosis were also studied. No differences in the skin reactions was found in children with bacterial infections, showing a score of 13 +/- 6 mm. But children with cystic fibrosis or with renal insufficiency exhibited a severe impaired cell-mediated immunity. To what extent the alteration of cell-mediated immunity affects the course of the various diseases, has to be investigated by further prospective studies.