All patients were nonsmokers with no other lung disease. All had refrained from using inhaled β2-agonists for > 2 weeks (indicating that β2-agonist tolerance would not affect the magnitude of bronchoprotection), and no patients were using controller medications. Study subjects were chosen only once, sequentially, as follows: 12 patients from one study2–; 7 patients from a second study3–; 6 patients from a third study4–; and 3 patients from a fourth study.5 The provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) was measured before and 10 min after inhaling 2 puffs (200 μg) of albuterol. The bronchoprotective effect of albuterol was expressed as the dose-shift,,2–5 which is the number of doubling concentrations that the PC20 had improved after albuterol administration. We examined the baseline FEV1 in the 10% strata, with 3 patients between 70 and 79% predicted, 8 patients between 80 and 89% predicted, 10 patients between 90 and 99% predicted, and 7 patients at ≥ 100% predicted.