Surfactant therapy was well tolerated (see Table 4 ), but only three of the trials reported any definitions or a priori criteria or of collecting adverse events [12, 21, 23] . Transient hypotension and transient hypoxia were the most commonly reported adverse events in the largest trial. These responded to a brief adjustment in ventilation, to a slowing of the rate of surfactant administration or to fluid administration. There was no difference in the incidence of air leaks in the two trials that reported this outcome. No patient was withdrawn from any of the trials because of adverse events. We did not pool the data on adverse events associated with the trial interventions from the six trials because of the inconsistent manner in which the events were documented and reported.