Two recent papers have addressed the ever-intriguing question of the role of eosinophils in asthma. Both groups used experimental models of airway inflammation in mice that were gene targeted to selectively ablate the eosinophil lineage. One group found that eosinophils were required for both airway hyperresponsiveness and mucus accumulation. The other demonstrated a 'critical role' for the cell in airway remodelling. The results, although largely confirmatory of previous studies both in mice and humans, put the eosinophil firmly back on the asthma stage and strengthen the case for developing effective eosinophil-depleting agents for clinical use.