We assessed the occurrence of early bronchial response and late bronchial response after the tread mill and free running exercise tests in 46 mild and moderate extrinsic asthmatics. On the treadmill 24 asthmatic subjects (52.1%) had an early post-exercise fall in PEF greater than ten percent and they were considered to have exercise induced asthma. In the free running 30 asthmatic patients (65.2%) had exercise induced asthma no asthmatic subjects showed a fall in PEF equal to or more than 20 percent during late response period. On control day PEF levels during this time were similar 4 to 13 hours post-exercise PEF values. We reported no significant correlation between early post-exercise PEF values and PEF levels during late response period after the treadmill and free running exercise tests. This study demonstrates the absence of a late response in EIA after the treadmill and free running exercise tests, at least in young people with mild or moderate extrinsic asthma.