Accessibility to health services is a major development problem facing sub-Saharan African countries. The prevalence of poverty and unemployment is a major hindrance to making health services accessible to the population especially the poor. Many development theories have been on how to make basic services affordable and accessible to the poor. The World Development Report 2004 focuses on making services work for the poor. The government of Ghana introduced nationwide National Health Insurance Scheme (NHIS) with the aim of providing health insurance and making health services accessible and affordable to the average Ghanaian. The 'cash and carry system' that existed before the introduction of the National Health Insurance Scheme made health services quite inaccessible to the poor. The 'cash and carry system' compelled patients to pay for the cost of health services before they were given the desired medication. The poor resorted to self-medication with its accompanied complications and problems. The overall objective of the study was to assess the contribution of the NHIS to health care delivery in the country and examine the sustainability challenges of the scheme. The study revealed that the NHIS has assisted in increasing Out-Patients-Department (OPD) attendance, reduction of self medication and made health services more assessable to the poor. It was however, observed that for a sustainable national health insurance scheme to be achieved, issues such as maintaining and expanding the client base, regular payment of the services providers and ensuring the requisite institutional capacity should be given the deserved attention.