Background: The U.S. Surgeon General advocates the accumulation of moderate-intensity activity throughout the day to improve health. Objective: To test the effectiveness of signs to encourage use of stairs instead of escalators. Design: Community intervention. Setting: Shopping center. Participants: 17 901 shoppers. Intervention: Signs promoting the health and weight-control benefits of stair use were placed beside escalators with adjacent stairs. Measurements: The sex, age, race, weight classification, and use of stairs were observed. Results: Overall, stair use increased from 4.8% to 6.9% and 7.2% with the health and weight-control signs, respectively. Younger persons increased their stair use from 4.6% to 6.0% with the health sign and 6.1% with the weight-control sign. Older persons almost doubled their stair use from 5.1% to 8.1% with the health sign and increased use to 8.7% with the weight-control sign. Differential use of stairs was observed between ethnic groups. Among white persons, stair use increased from 5.1% to 7.5% and 7.8% with the health and weight-control signs, respectively. Among black persons, stair use decreased from 4.1% to 3.4% with the health sign and increased to 5.0% with the weight-control sign. At baseline, lean persons used the stairs more often than overweight persons (5.4% and 3.8%, respectively). The health sign increased stair use to 7.2% among normal- weight persons and 6.3% among overweight persons; the weight-control sign prompted stair use to increase to 6.9% among persons of normal weight and to 7.8% among overweight persons. Conclusions: Simple, inexpensive interventions can increase physical activity. Research is needed to identify effective motivators to promote activity among black persons.