Epidemiological data indicate that the prevalence and severity of asthma is higher among females than males after puberty. The influence of sex on asthma incidence suggests that sex hormones could play a role in the pathogenesis of the condition associated with asthma. However, the mechanisms of the affect of sex are not clear. Therefore, in the current study, we investigated the sex differences in allergic inflammation in terms of lymphocyte function, using a murine model of allergic asthma. In either BALB/c or C57BL/6J mice, the airway inflammation in female mice sensitized with OVA followed by OVA inhalation was more severe than that in male mice. The contents of Th2 cytokines, such as IL-4, IL-5 and IL-13, in bronchoalveolar lavage fluid from female mice were significantly increased compared with male mice. The airway inflammation in female mice after adoptive transfer of splenocyte from sensitized female mice was more severe than that in any other combination of donors and recipients. Furthermore, splenocytes from sensitized female mice produced more Th2 cytokines than those from sensitized male mice, upon stimulation with OVA. The degree of airway inflammation induced by lipopolysaccharide inhalation was not significantly different between male and female mice. Our findings suggest that sex differences in allergic airway inflammation are due to those in not only sex hormones but also lymphocytes function