Millions of seniors are flocking to Medicare risk health maintenance organizations, or HMOs. Yet, relatively little is known about how well these HMOs serve their Medicare enrollees. This paper will explore the phenomenal growth of these health plans, the reasons for such growth and the strain it has caused on the HMO infrastructure. Early indications suggest that seniors encounter three problem areas with relative frequency. First, seniors face an information void when choosing among competing HMOs. Secondly, beneficiaries report difficulties obtaining access to home health and emergency care. Finally, beneficiaries who want to appeal their HMOs' decisions to deny care have trouble negotiating their way through a complicated, delay-ridden appeals process.