Recently, much attention has been given to the possible role of lymphocytes and their soluble products in causing and maintaining allergic inflammation. The aim of this study was to assess the production of mRNAs for interleukins (IL) in bronchoalveolar lavage (BAL) cells obtained from allergic asthmatics after challenge with the relevant allergen in the period between early and late reactions. We evaluated BAL fluid cells obtained from six asthmatic subjects and four nonatopic controls. Challenge was performed with the relevant allergen. BAL fluid cells were obtained by fiberoptic bronchoscopy and bronchoalveolar lavage. To detect mRNA encoding each cytokine in BAL cells we used a reverse transcriptase polymerase chain reaction method. We evaluated IL-1 alpha, -2, -4, -5, -6, -13, and granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon-gamma (IFN-gamma). mRNAs for IL-1 alpha, -2, -4, -5, and IFN-gamma were detected in all of the atopic subjects; mRNAs for IL-6 and GM-CSF were found in five asthmatics; and mRNA for IL-13 was found in one patient only. In contrast, no mRNAs for IL-2, -4, -5, -6, -13, and GM-CSF were detected in the nonatopic healthy controls; mRNA for IL-1 alpha was found in one out of four normal subjects; and mRNA for IFN-gamma was evidenced in two of four subjects. The cellular environment in BAL fluids from allergic asthmatics before the clinical appearance of the late airway reaction shows an unrestricted expression of mRNA for cytokines. The local cytokine milieu could have an important role in the modulation of bronchial inflammation and in the appearance of allergic symptoms.