This paper reports the development and validation of the Neighborhood Observation Scale, a 41 item measure of neighborhood physical appearance, social appearance, safety, and amenities. Three independent ratings were collected on each of 244 neighborhoods in 132 census block groups in five South Carolina counties, for a total of 732 observations. Inter-rater reliability analysis showed 92.6% agreement among at least two raters and an intraclass correlation of 0.54, indicating acceptable reliability. Exploratory factor analysis extracted eight factors for neighborhood physical appearance, school/park/public space physical appearance, neighborhood social appearance, indicated social engagement, observed social engagement, park/public space social engagement, resident watchfulness, and neighborhood safety risk. A follow-up confirmatory factor analysis supported the eight factor structure. Reliability analysis produced alpha coefficients ranging from 0.55 to 0.94 for the eight factors, indicating reliability for use as sub-scales. Convergent validity was determined by generally acceptable correlations of the factor sub-scales with measures of neighborhood distress, rates of child maltreatment and ICD-9-CM coded child injuries, and resident perceptions of neighboring, collective efficacy, reciprocal helping, and children's safety in the home. Implications for research and policy and program development are discussed.