In this study we investigated a possible relationship of delayed type hypersensitivity (DTH), as a model for cellular IgE-independent immunity, with the induction of airway hyperreactivity. In PC1 (picryl chloride) sensitized BALB/c mice DTH-like lung infiltrates were found that were maximal 48 hr after intranasal hapten challenge. During the elicitation of this DTH-like reaction tracheal hyperreactivity to the cholinergic agonist carbachol could be detected from 2 hr after challenge with the homologous hapten and that was maximal after 48 hr.