In response to the evidence that fenoterol was a major cause for the second epidemic of asthma deaths in New Zealand, the Department of Health severely restricted its availability, thereby allowing an 'experiment in prevention' to be undertaken. These regulatory actions, which effectively removed fenoterol from the market in New Zealand, were associated with a sudden and marked reduction in asthma mortality, providing further evidence for a causative role of fenoterol in the epidemic of asthma deaths in New Zealand.