Research Findings: This study examines child care centers that improved quality and sustained these improvements over time. Quality was assessed using the Early Childhood Environment Rating Scales (ECERS). Forty-three centers were visited three times over six years. Centers that substantially improved by Time 2 were not initially rated better than those that did not improve but did employ less harsh teachers. At the second visit, centers that improved substantially were higher in quality, employed more sensitive and less harsh teachers, had experienced lower teaching staff turnover, and achieved NAEYC accreditation. The vast majority sustained these improvements. Centers seeking NAEYC accreditation were more likely to become accredited if they received moderate to intensive support and experienced less teaching staff turnover. Centers were more likely to experience lower turnover if they paid staff higher wages. Practice or Policy: Resources to support centers in becoming accredited and to increase the retention of teaching staff can assist centers in improving and sustaining quality.