We prospectively assessed the association of neighborhood socioeconomic status (SES) with 10-year weight change and with incident obesity among 48,359 women in the Black Women's Health Study (BWHS). Lower neighborhood SES was significantly associated with 10-year weight gain after adjustment for individual SES and behavioral variables, such as physical activity and caloric intake. Low neighborhood SES was also associated with increased incidence of obesity during 10 years of follow-up among women of normal weight at baseline (BMI <25 kg/m2). The associations were most evident among BWHS participants who had graduated from college. These prospective data suggest that lower neighborhood SES contributes to overweight and obesity in African-American women.