The haemophagocytic syndrome (HPS) is a rare but frequently fatal disorder of immune regulation caused by hypercytokinemia. Using cytometric bead array technique, the serum T‐helper cell type 1 (Th1) and 2 (Th2) cytokines including interferon‐γ (IFN‐γ), tumour necrosis factor (TNF), interleukin (IL)‐10, IL‐6, IL‐4 and IL‐2 were determined in 24 children with de novo HPS and 87 children as control. The median levels of serum IFN‐γ, IL‐10 and IL‐6 in the acute phase of HPS were 901·7, 879·0 and 63·8 pg/ml, respectively, significantly higher than those after remission, and in the healthy volunteers and patients with viral infection. IL‐4 was slightly elevated while IL‐2 and TNF were within normal range in acute phase. Patients with bacterial sepsis showed an extremely high level of IL‐6 and moderate level of IL‐10, whereas IFN‐γ was only slightly elevated. Five patients were diagnosed with HPS according to the Th1/Th2 cytokine pattern 3–13 d earlier than they fulfilled the relevant diagnostic criteria. IL‐10 level >2000 pg/ml was an unfavorable prognostic factor for HPS treatment response (P = 0·033) and outcome (P = 0·009). We conclude that the significant increase of IFN‐γ and IL‐10 and a slightly increased level of IL‐6 is an early, specific and prognostic cytokine pattern for childhood HPS.