Rationale: Asthma is a chronic inflammatory disease of the small airways, with airway hyperresponsiveness (AHR) and inflammation as hallmarks. Recent studies suggest a role for arginase in asthma pathogenesis, possibly because arginine is the substrate for both arginase and NO-synthase (NOS) and because NO modulates bronchial tone and inflammation. Objective: To investigate the importance of increased pulmonary arginase 1 expression on methacholine-induced AHR and lung inflammation in a mouse model of allergic asthma. Methods: Arginase 1 expression in the lung was ablated by crossing Arg^fl/flwith Tie2Cre^tg/- mice. Mice were sensitized and then challenged with ovalbumin. Lung function was measured with the Flexivent. Adaptive changes in gene expression, chemokine and cytokine secretion, and lung histology were quantified with qPCR, ELISA, and immunohistochemistry. Results: Arg1 deficiency did not affect the allergic response in lungs and large-airway resistance, but improved peripheral lung function (tissue elastance and resistance), attenuated adaptive increases in mRNA expression of arginine-catabolizing enzymes Arg2 and Nos2, arginine transporters Slc7a1 and Slc7a7, chemokines Ccl2 and Ccl11, cytokines Tnfa and Ifng, mucus-associated epithelial markers Clca3 and Muc5ac, and lung content of IL13 and CCL11. However, expression of Il4, Il5, Il10, and Il13 mRNA, lung content of IL4, IL5, IL10, TNFα, and IFN protein, and lung pathology were not affected. Correlation analysis showed that Arg1 ablation disturbed the coordinated pulmonary response to ovalbumin challenges, suggesting arginine (metabolite) dependence of this response. Conclusion: Arg1 ablation in the lung improved peripheral lung function and affected arginine metabolism, but had little effect on airway inflammation.