Group B streptococcus (GBS) is a leading cause of neonatal morbidity and mortality in the United States. In 2002, CDC, the American College of Obstetricians and Gynecologists (ACOG), and the American Academy of Pediatrics (AAP) issued revised guidelines for the prevention of perinatal GBS disease. These guidelines recommend universal screening of pregnant women by culture for rectovaginal GBS colonization at 35-37 weeks' gestation and the use of intrapartum antibiotic prophylaxis for GBS carriers. To examine rates of neonatal and pregnancy-associated GBS disease after the revised guidelines were issued, CDC analyzed surveillance data from the Active Bacterial Core surveillance (ABCs) system from the period 2003-2005 and compared them with data from 2000-2001, the period immediately preceding the universal screening recommendations. This report describes the results of that analysis, which indicated that annual incidence of early onset GBS disease (i.e., in infants aged 0-6 days) was 33% lower during 2003-2005 than during 2000-2001. However, although incidence among white infants decreased steadily during 2003-2005, incidence increased 70% among black infants. Incidence of GBS disease among infants aged 7-89 days (i.e., late-onset disease) and pregnant women remained stable after revised universal screening guidelines were issued. Continued surveillance is needed to monitor the impact of the guidelines on perinatal GBS disease and trends in racial disparities and to guide interventions to reduce disparities.