Purpose: Declines in physical functioning (PF) among elderly cancer patients threaten quality of life and the ability to maintain independence. Adherence to healthy lifestyle behaviors may prevent functional decline. Patients and Methods: Project Leading the Way in Exercise and Diet (LEAD), an intervention development study of the Pepper Older Americans Independence Center, aimed to determine whether breast and prostate cancer survivors (age 65+ years) assigned to a 6-month home-based diet and exercise intervention experienced improvements in PF when compared with an attention control arm receiving general health information. An accrual target was set at 420, and PF (Short Form-36 subscale), physical activity (Community Healthy Activities Models Program for Seniors), and diet quality (index from 3-day recalls) were assessed at baseline and at 6 and 12 months (6 months after intervention). Results: This developmental project did not achieve its accrual target (N = 182); however, PF change scores were in the direction and of the magnitude projected. Baseline to 6-month change scores in the intervention versus the control arms were as follows: PF, +3.1 v -0.5 (P = .23); physical activity energy expenditure, +111 kcal/wk v -400 kcal/wk (P = .13); and diet quality index, +2.2 v -2.9 (P = .003), respectively. Differences between arms diminished during the postintervention period. Conclusion: These findings suggest that home-based diet and exercise interventions hold promise in improving lifestyle behaviors among older cancer survivors, changes that trend toward improved PF. Future studies should incorporate larger sample sizes and interventions that sustain long-term effects and also take into account secular trends; these efforts will require adequate planning and resources to overcome the numerous barriers to intervening in this difficult to reach yet vulnerable population. © 2006 by American Society of Clinical Oncology.