The inflammatory response induced by the conditioning regime may be related to the outcome in allogeneic stem-cell transplantation (SCT). However, previous statements concerning the prognostic significance of cytokine measurements during conditioning have not been conclusive. We investigated a broad range of cytokines in plasma samples drawn daily immediately before start of pretransplant conditioning and during the conditioning. The presented data indicate that single-day measurements of inflammatory cytokines during conditioning may lead to unreliable conclusions concerning their prognostic significance. However, serial quantitation of soluble tumour necrosis factor receptor I (sTNFRI) is more likely to reflect the degree of inflammatory activation induced by pretransplant conditioning.