The concern for food security is a cornerstone in the development process for every country. This dissertation is examining food security from three perspectives. First, chapter one explores the most important economic and developmental factors leading to food security and combines these factors in an index to measure the change in food security levels over time for different countries. The next chapter then uses this index to determine whether food security is related to dietary diversity. Finally, the third chapter is a descriptive study of food security in Saudi Arabia.The first part of this research employs principal component analysis (PCA) in order to build a food security index. The objective of the analysis is to provide the variables that build a food security index and the method to weigh them, which allows a national-level comparison of countries from different parts of the world. These data will be used in subsequent parts of this research to study the association between the overall food security index and the four pillars of food security with dietary diversity at the national level in different countries. To build the index, PCA was used to evaluate the contribution