We used a 2-week trial of prednisolone to determine “target” lung function for subsequent asthma therapy. The aim of this study was to evaluate whether some children exceed their “target” forced expired volume in 1 sec (FEV1) on subsequent visits in the following year, and whether this is associated with particular clinical or pathological features. Children (aged 6–16 years) with difficult asthma underwent spirometry and exhaled nitric oxide (FENO) measurements before and after 2 weeks of prednisolone 40 mg/day. At the end of the course, subepithelial eosinophils and reticular basement membrane thickness were assessed. The highest FEV1 obtained in a 1-year follow-up was compared with the poststeroid postbronchodilator (“target”) FEV1. Four of 22 children (18%) demonstrated an increase of >9% above their “target” FEV1 during follow-up. None of these children had been prescribed additional asthma medications. Three of 7 children with persistent airflow limitation (PAL; poststeroid postbronchodilator FEV1 80% predicted during follow-up. The median (interquartile range) number of subepithelial eosinophils was significantly higher in children who exceeded their target FEV1 than in children who did not (12.4 (8.5–39.9) vs. 1.4 (0.0–4.8) cells/mm2, P = 0.018). In conclusion, a 2-week course of prednisolone is not necessarily predictive of “target” lung function. Definitions such as PAL should be regularly reviewed on individual basis. Pediatr Pulmonol. © 2005 Wiley-Liss, Inc.