Background: sFasL is the soluble form of FasL inducing apoptosis by binding to Fas. Fas/sFasL could be the most important mechanisms in inflammatory conditions such as asthma by controlling inflammatory responses.This study was undertaken to determine the level of sFasL in allergic and non- allergic asthmatic patients with different stages of asthma control.Methods: Twenty asthmatic patients were enrolled and divided into controlled and uncontrolled patient groups.They were divided into 4 subgroups including controlled/allergic, controlled/non-allergic, uncontrolled/allergic and uncontrolled/non-allergic subgroups. Five normal subjects were selected as a control group. From all subjects, 3 ml of blood was obtained and sFasL and IgE serum levels were evaluated by a specific ELISA kit.Results: sFasL in the controlled and uncontrolled patient groups did not have any significant difference, but in the uncontrolled/allergic subgroup, it was significantly lower than that in the control group and also higher in the uncontrolled/non-allergic subgroup insignificantly.Conclusion: In patients with acute inflammatory conditions, sFasL had an increasing effect to control inflammation observed in uncontrolled/non-allergic subgroup, but unexpectedly not in the uncontrolled/allergic subgroup.Probably in allergic patients, there are factors or mechanisms that inhibit sFasL production or expression.