The incomplete block designs are widely used in various fields such as Agriculture, Genetics, Engineering and Industry to name a few. This book presents some aspects of construction and analysis of incomplete block designs in a simplified and practical approach. The analysis of PBIB designs with two or more associate classes is presented without using the secondary parameter. Incomplete block designs with small number of replications say two or three are required for many practical situations. The construction and analysis of an incomplete block designs with three replications is presented. Some constructions of rectangular designs are described and two useful series of G.D.designs are obtained. The duals of some PBIB designs with two associate classes are obtained. A useful relation between the efficiency factors of the original design and dual design is derived. The use of this relation in partial diallel crosses is also discussed. This book is specifically useful for those who are engaged in applied research and also for those who are involved in teaching and research on the subject.