Micro and Small Enterprises (MSEs) are currently recognized as a real engine of economic growth and technological progress since they are effectively using the skill and the talent of the people without requesting high-level training, much capital and sophisticated technology. However, a large number of MSEs are unable to grow and remain survival type since start up. Because the growth of MSEs is subject to different dynamic forces. Therefore, this book provides an insight in to the critical determinants of MSEs growth in Northern Ethiopia in which MSEs that are started operation with better initial investment size, located at out of town and owned by male are growing rapidly than those MSEs that are started operation with relatively small initial investment size, located at main road side and owned by women. In addition, MSEs that are engaged in manufacturing sector grow faster than those that are engaged in service or trade sectors. So that this analysis will help national and international organizations that are concerned with unemployment reduction and poverty alleviation through the promotion and development of MSEs at all levels.