Thirty-one neonates with early onset of serious group B streptococcal infections were observed in a four-year period. The mortality was 52%. Premature infants with clinical signs of respiratory distress syndrome were at highest risk of death; clinical signs of RDS were typical until apnea, shock, respiratory failure, and worsening of the radiographic pattern unexpectedly intervened. Pathologic material from infants with radiographic evidence either of RDS or of pneumonia showed both typical hyaline membrane disease and pneumonia in most instances. Factors which may be helpful in recognizing premature infants at risk for GBS disease in the much larger group of premature infants with uncomplicated RDS include: history of artificial, premature, or prolonged rupture of membranes; localized pulmonary infiltrates on chest roentgenogram; low absolute neutrophil count; and an unusually rapid progression of RDS.