Livestock production in developing countries has begun getting much attention from governments, donor agents and researchers. In many countries cash crops constituted the major source of foreign exchange earnings and thus got much more attention than livestock production. However, the 1970's were generally a period of falling prices for most of the major cash crops (coffee, cocoa, cotton, sisal, etc.). The critical need for turning to other foreign exchange earning commodities, the need to reduce the importation of manufactured foodstuffs and the growing demand for animal proteins plus the pressure to improve the living conditions of the usually less privileged pastoral and agripastoral communities requires full understanding of the production potentials and constraints in their respective production systems. The study set out to bring together the current literature on herd structure, production traits and cattle transactions of zebu herds in tropical Africa. Specifically the study examines the herd characteristics and productivity of W'Arusha zebu herds in N. Tanzania. The first chapter includes the problem statement, objectives and limitations of the study. In the second chapter, an introduction to Tanzania is made covering geographic, economic and social characteristics. The geographical, historical, and production conditions of the W'Arusha and the data collection methodology are presented. The most important parts of the study are contained in chapter 3, 4, and 5. In chapter 3, literature, covering a wide range of production systems and management conditions is reviewed. Chapter 4 reports the results of the study from the W'Arusha sample herd. Chapter 5 presents the results of the regression analysis and herd growth simulations. Chapter 6 presents the conclusion from the study based on the literature and the findings from the sample herd. Some recommendations for further research, especially, covering the economics of production in livestock system are presented.