The administration of beta-mimetic drugs to pregnant women poses the problem of possible long-term repercussions in the children born to these mothers. 42 children from women who had been treated with 60-80 mg a day of ritodrine hydrochloride (Pre-par), during a period varying from 3 to 93 days, were closely matched with infants from untreated mothers. Each child, (aged from one to 3 years), was fully investigated on the basis of: a detailed questionnaire to the mother; careful clinical examination; assessment of psychomotor development; the Denver test; electrocardiography and urine analysis. There was no statistically significant difference between the two groups for any of the variables of development that were studied. One child had left ventricular hypertrophy, which was probably incidental. It is concluded that administration of ritodrine hydrochloride to pregnant women induces no harmful long-term effects in their offspring.