Summary The prophylactic value of beta‐mimetic drugs in preventing respiratory distress syndrome (RDS) is investigated by comparing 29 preterm infants of ritodrine treated mothers with 34 preterm infants of a control group. Five cases of RDS (17 per cent) occurred among the infants of treated mothers as compared with 12 cases (35 per cent) in the control group (p=0.09). The difference is, however, statistically significant for the group of infants weighing less than 2300 grams (p=0.01) which includes all infants affected with RDS.