The mortality and morbidity for all 255 live births of infants with birth weight 501 to 1000 gm and delivered to residents of a geographically defined region between 1977 and 1980 are reported. In all, 117 (46%) infants were discharged alive; there were four postdischarge deaths, and three infants were lost to follow-up. The mean birth weight and gestational age of the survivors was 850 +/- 118 gm and 27.1 +/- 2 weeks, respectively. Neurosensory handicaps were detected in 26 (24%) of 110 survivors followed for a minimum of 2 years corrected age. In addition, 29 (26%) infants had nonneurologic problems and 55 (50%) were considered apparently normal. Within 100 gm birth weight groups, survival improved significantly with increasing birth weight, but the handicap rate among survivors remained relatively constant. These figures are proposed for use in describing the current prognosis at birth for liveborn tiny infants from comparable unselected populations.