Rural-urban differentials in fertility behaviour are neither new nor surprising, but a difference of over four children per woman as observed between rural Ethiopia and the country's national capital, Addis Ababa, in 1990 is rare, possibly unique. Reported fertility in Addis Ababa in 1990 was about 2.6 children per woman. By the mid-1990s, it declined further to 1.8 children per woman. This study investigates the dimensions, components and causes of this remarkable reproductive change. ¶ The study specifically asks and seeks to answer the following questions. Is the decline real, or is it merely an illusion created by faulty reporting? If it is real, how has it come about? Did it result from a change in the onset of reproduction or a decline in the proportion of women reaching high parities or both? And in what context has such a fundamental, even revolutionary, change taken place in a country and a continent that are mostly yet to join the global transition to a small family-size norm. ¶ Data for the study were drawn from two national population censuses, undertaken in 1984 and 1994, two fertility surveys, conducted in 1990 and 1995, and a number of supplementary sources, including a qualitative study conducted by the investigator. Results from the study confirm that the trend of declining fertility and the recent fall to below-replacement-level are indeed real. As the analysis shows the decline was largely driven by changes in the marriage pattern, and supplemented by the increased propensity of fertility control observed across all birth orders and age groups. All socio-economic groups in the city have had a decline in cohort fertility and this was brought about both by shifts in population composition (a composition effect) and increased intensity of fertility control within each group (a rate effect). The institutional and cultural factors that are believed to have prompted these changes are discussed in the thesis in some detail.