Although recent technologic advances have dramatically improved the survival of preterm infants, little information exists regarding the attitudes of neonatologists toward their smallest patients, infants born at the "limit of viability." In this pilot study we sent a single mailing of a 25-question survey designed to provide information about the medical treatment of extremely preterm infants (< 22 to 27 weeks' gestational age) to 3056 neonatologists practicing in the United States in September 1992. The 1131 (37%) respondents were well distributed geographically and by nature of practice (i.e., academic, academic affiliate, and community hospitals). Most of the respondents counseled parents that all infants < or = 22 weeks' gestational age die and that at least 75% of infants born at 23 weeks' gestation die. Only for infants born at > or = 26 weeks' gestational age did most of the neonatologists counsel parents that mortality is < or = 50%. Nonintervention or compassionate care in the delivery room was believed to be appropriate for infants less than 23 weeks' gestational age by virtually all neonatologists, by 52% of respondents for infants 23 weeks' gestational age, and by only 1% of respondents for infants 25 weeks' gestational age. Approximately two thirds of neonatologists considered parental wishes regarding resuscitation, and one quarter considered parental parity/fertility history in their medical decision making for infants born at 23 to 24 weeks' gestation. If an infant who had been previously resuscitated decompensated in spite of maximal medical treatment, most of the neonatologists were not willing to provide full resuscitation for infants born at any gestation less than 27 weeks. However, the number of neonatologists who would actively encourage withdrawal of support in a decompensating infant decreased markedly for infants born at > or equal 25 weeks' gestation. Neonatologists who responded to this survey in 1992 considered 23 to 24 weeks of gestation the limit of viability and had great concerns regarding medical decision making for these infants.