Climate change is the most serious problems facing humans and global sustainable development. In this book rainfall variability is the major concern. The study aims to assess the spatial and temporal variability and trend of rainfall in all year round rainfall region of Ethiopia. To achieve the objective, nineteen rainfall indices were defined and analyzed for trends on daily time series for nine stations over the period 1978-2007. Kendall-tau trend test shows two distinct trends: i) Decreasing trends in annual total rainfall amount, short wet spells, very heavy precipitation days and daily rainfall exceeding 95th and 99th percentiles at Gore; ii) Increasing trends in annual total rainfall amount, frequency of heavy precipitation days, very heavy precipitation days and long dry spells at Jimma. These are the indications of recent prevalence of dry spells/drought periods to the wettest part of Ethiopia. Generally the findings imply that climate variability and change requires urgent attention and action to tackle its impacts on economy, social and environment in south western part of Ethiopia.