• Before the whole-cell pertussis vaccine was available, Bordetella pertussis infections were an important cause of morbidity and mortality in infants. To determine the extent of continuing morbidity in an era of vaccination, a retrospective review was conducted of the records of neonates and infants hospitalized with pertussis infection at Parkland Memorial Hospital and Children's Medical Center, Dallas, Tex. During the 20 years from 1967 through 1986, 182 patients were younger than 24 months. Among 176 patients whose immunization history was recorded, 89% had received fewer than two doses of pertussis vaccine. The mean hospital stay was 7.4 days (range, 1 to 69 days). A convulsion occurred in 11 patients (6%). Apnea was reported in 45 patients (25%) and observed in the hospital in 26 (14%). Nine patients (5%) received mechanical ventilatory therapy. Intensive care monitoring was required in 18 patients (10%). Three (1.6%) died, all with secondary bacterial pneumonia. This hospital-based population indicates that pertussis continues to be a cause of serious morbidity and mortality in infants.