Recently, it has been reported that beta-adrenoceptor agonists containing a catechol moiety, reduce hydrogen peroxide production by alveolar macrophages, an effect suggested to be due to scavenging by the catecholamines of superoxide, the precursor of hydrogen peroxide. However, catecholamines interfere with the method used, in that study, to determine hydrogen peroxide formation. We re-examined the obtained results using two independent methods for measuring hydrogen peroxide that are not affected by catecholamines. We found that catecholamines, in a concentration up to 10(-5) M, had no effect on hydrogen peroxide formation out of superoxide. It was, furthermore, established that reduction of hydrogen peroxide formation by scavenging of superoxide by catecholamines is not very likely.