Objectives. To study the correlation between serum concentrations of adrenocorticotrophic hormone (ACTH) and cortisol in relation to severity of disease in children with meningococcal sepsis. Methods. Subjects were children with meningococcal sepsis, admitted to the pediatric intensive care unit. Clinical data, laboratory values and blood samples were selected. Arterial cortisol, ACTH, interleukin 6 and tumor necrosis factor alpha concentrations were measured on admission and studied for their relation to severity of disease (sepsis, septic shock/survivors, septic shock/nonsurvivors). Results. Seventy-two patients fulfilled the criteria for meningococcal sepsis. Sixty-two of these children with positive blood cultures of Neisseria meningitidis, who were not treated with corticosteroids before admission, were included. Fifty of the 62 patients had septic shock. Twelve of those children (24%) died. The median age of the subjects was 2.6 years (range, 0.3 to 16.1 years). Cortisol values were significantly lower in non-survivors (median, 654 nmol/l) than in survivors (median, 2184 nmold) nmol/l) (P > 0.01). ACTH values were significantly higher in children who died (median, 1271 ng/l) than in survivors (85 ng/l) (P < 0.01). The median cortisol:ACTH ratio decreased significantly depending on the disease severity categories. Conclusions. Low serum cortisol concentrations in combination with high ACTH concentrations are associated with poor outcome in children with severe meningococcal disease.