The relationship between a four-group health promotion intervention program and the subsequent medical costs were analyzed for a group of 1,188 employees in a northern California utility company. Results suggest strong associations between health promotion interventions and the subsequent reduction in medical costs related to hospital days, doctor visits, and sick days, based on different cost estimates. As health promotion intensified, from group 1 (assessment-only control), group 2 (low-intensity intervention focusing on self-care), group 3 (medium-intensity intervention focusing on group support), to group 4 (high-intensity intervention targeting high-risk individuals), benefits seemed to increase accordingly from $145 per person for group 1 to $421 per person for group 4, based on the medium cost estimate. Cost-benefit analysis demonstrates that medium-intensity intervention (group 3) appears to have contributed to a greater level of medical cost reduction, per dollar spent, than all other intervention groups.