Preferred Provider Organization. A health care organization composed of physicians, hospitals, or other providers which provides health care services at a reduced fee. A PPO is similar to an HMO, but care is paid for as it is received instead of in advance in the form of a scheduled fee. PPOs may also offer more flexibility by allowing for visits to out-of-network professionals at a greater expense to the policy holder. Visits within the network require only the payment of a small fee. There is often a deductible for out-of-network expenses and a higher co-payment. A policy holder will have a primary physician within the network who will handle referrals to specialists that will be covered by the PPO. After any visit, the policy holder must submit a claim, and will be reimbursed for the visit minus his/her co-payment.