Invasive bacterial infections encompass clinical diagnoses of septicemia, pneumonia, and meningitis. Together, these infections are termed "neonatal sepsis" and account for over half of the newborn deaths at the district and sub-district level in India. Sepsis is the most common (80-90 percent) primary diagnosis for admission in Indian hospitals. Phase 1 of this study is a prospective, epidemiologic study involving over 1,000 community-based and hospital populations of newborn infants. It includes identifying all infants born in study hospitals and those brought to the hospitals with suspected sepsis; obtaining blood cultures from these infants and identifying the sepsis-causing bacteria; screening of all bacterial strains isolated from blood cultures for antimicrobial resistance; collecting basic demographic, risk factor, and treatment data on each case; and developing a computer-based system/network for data management. A village-level surveillance system was put in place to identify women during their pregnancy; monitor pregnancy outcomes; and establish a mechanism for referral of all potentially septic infants to participating clinics or hospitals for evaluation, including the collection of blood cultures. Potential sources of bacteria causing sepsis will be identified using molecular epidemiologic techniques. This involves matching septic infants' blood isolates with other colonizing isolates obtained from screening skin, throat, and stool cultures in the infant and skin and vaginal cultures from their mothers.