Today, approximately one-fourth of the world’s population includes 1,620 million persons who are part of the expanding Islamic Ummah. Muslims are found in large numbers in all regions of the world but are concentrated in Africa, Asia, the Middle East and selected successor states to the former Soviet Union. Despite the obvious wealth of some Islamic nations most Muslims live under conditions of poverty, joblessness, illiteracy, ill health, social and political unrest and, in some regions, religious extremism. Using the extensively pre-tested Weighted Index of Social Progress, this paper reports a 40-year time series analysis of the nature, extent, and pace of social change that is taking place within 53 of the 57 member states of the Organization of Islamic Cooperation (OIC). Data are reported at four levels of analysis. Selected data also are reported for both the OIC-as-a-whole and for the world-as-a-whole. The present analysis offers a sometimes bleak, but generally optimistic, picture of the dramatic differences that characterize development patterns within Islamic countries, subregions, and regions. Particular attention is given to: (a) the legacy of colonialism that persisted for some OIC states until as recently as 1991; (b) the recurrent social unrest that continues to characterize development in many Islamic states, e.g., the “Arab Spring” (Vision of Humanity 2012); (c) the presence or absence of marketable natural and human resources; and, (d) the significant contributions being made to the development of Islamic countries by the United Nations’ Millennium Development Campaign (United Nations 2005) and the OIC’s Ten-Year Programme of Action (OIC 2005). However, the important social gains reported in this paper for some countries and geographic regions remain highly variable, potentially reversible, unless the collective wishes of Islamic nations are translated into concerted actions both within OIC member states and the larger world community of nations.