['To compare plasma levels of thioredoxin (Trx), TNF-alpha and IL-1 beta in children during the acute phase of meningococcal septic shock (MSS) and in convalescence.', 'Retrospective, observational study in the paediatric intensive care unit of a postgraduate teaching hospital.', 'Thirty-five children requiring intensive care for meningococcal sepsis; paired convalescent samples from 30 survivors (median interval between samples 62 days); 25 healthy control children.', 'Plasma Trx levels were significantly lower in the children with MSS, both during the acute illness (5.5 ng/ml, IQR 1.4-11.4) and in convalescence (2.5 ng/ml, IQR 0.4-6.9) than controls (18.8 ng/ml, IQR 7.9-25.0). Levels of IL-1 beta and TNF-alpha were higher in patients with acute MSS (30.3 pg/ml, IQR 3.6-63.6, and 145.9 pg/ml, IQR 31.8-278.1 respectively) than controls (3.7 pg/ml, IQR 0-36.9, and 23.8 pg/ml, IQR 0-124.3, respectively). Levels fell in convalescence (3.7 pg/ml, IQR 0-25.5, 3.7 pg/ml, IQR 0-304.8, respectively). Plasma Trx was higher in non-survivors, albeit a small group (n=5), than in survivors (n=30). Trx, IL-1 beta, and TNF-alpha levels were not correlated with predicted mortality as assessed by the paediatric risk of mortality (PRISM) score.'] Is persistently low plasma thioredoxin associated with meningococcal septic shock in children?