To determine the effect of "warm-up" on exercise-induced asthma (EIA) 18 subjects ( mean age 19.7 years) performed five minutes of submaximal treadmill running to achieve a heart rate (HR) of 85% of predicted maximum for age. One such exercise test was preceded by "warm-up" and one was not. "Warm-up" consisted of three minutes of treadmill walking or jogging to attain 60% of predicted maximun HR for age. An identical incidence (77.8%) and severity (38.1% mean decrease in FEV1) of EIA was recorded after treadmill running whether preceded by "warm-up" or not. While this study does not support the concept that "warm-up" could reduce the likelihood of EIA, it is recommended that a longer, more intense "warm-up" involving interval exercise should be evaluated before rejecting the view that "warm-up" ameliorates EIA.