The incidence of hyaline membrane disease in 41 preterm infants born between January 1975 and January 1976 was investigated in a retrospective study. Terbutaline, a beta2-receptor stimulating drug, had been administered to the women in order to arrest premature labour. In spite of the treatment 24 preterm infants were delivered. The incidence of HMD in this group was 1/24. In a group of 17 neonates whose mothers had received no such treatment the incidence of HMD was 5/17. Comparison between the two groups revealed a significantly lower incidence of HMD in the terbutaline treated group than in the controls (p less than 0.05). There were no significant differences in maternal age, gestational age, birth weight or Apgar score between the two groups. The lower incidence of HMD in the terbutaline treated group is suggested to reflect a rapidly induced release of pulmonary surfactants in the preterm infants. Evidence for a similar sequence of events has earlier been shown to occur in animals under standardized experimental conditions.