CONTEXT: Healthy diets and regular physical activity confer many health benefits, but the prevalence of these behaviors is relatively low. BACKGROUND: Cost-effective strategies are needed to increase healthy eating and physical activity in the population. DESIGN: An RCT, conducted in 2006, of a 16-week e-mail program offered individually tailored, small-step goals; a personal homepage with tips; educational materials; and tracking and simulation tools. SETTING/POPULATION: Seven hundred eighty-seven employees in the administrative offices of a large healthcare organization volunteered to participate. MAIN OUTCOME MEASURES: Changes were self-reported for total physical activity; moderate physical activity (MPA); vigorous physical activity (VPA); walking; sedentary behavior; and intake of fruits and vegetables, saturated and trans fats, and added sugars in the intervention group compared to the control group. RESULTS: In intent-to-treat analyses (conducted in 2007 and 2008) that set change in nonresponders to the follow-up questionnaire to zero, the intervention group reported increases of 28.0 minutes/week (min/wk) of MPA (SE=7.4, p=0.0002); 12.5 min/wk of VPA (SE=5.7, p=0.03); and 21.5 min/wk of walking (SE=5.5, p=0.0003) relative to the control group. Intake of both saturated and trans fats (grams/day [g/day]) declined (beta=-0.95, SE=0.36, p=0.01; beta=-0.29, SE=0.12, p=0.02, respectively). The consumption of fruits and vegetables increased significantly (p=0.03), and the consumption of added sugars decreased marginally (p=0.08). The largest changes were in participants who did not meet behavioral recommendations at baseline (increase of 55.4 min/wk of MPA and decrease of 1.15 g/day of trans fats, relative to the control group). Differences between the intervention and control groups were still observed 4 months after the intervention ended. CONCLUSIONS: ALIVE is an effective program for achieving significant improvement in diet and physical activity. TRIAL REGISTRATION: NCT00607009.