Infectious diseases of livestock are major constraints in enhancing the productivity and economic returns. Besides vaccines, accurate, reliable, rapid, sensitive & cost effective diagnostic procedures are very important for control. A number of bacterial diseases causes a very heavy economic loss to the livestock sector due to lack of appropriate diagnostic kits with the persons related with the diagnosis. Although, advanced countries have been successful in developing and using diagnostic kits, these are very expensive and are not affordable due to poor economic status of the livestock owners. Therefore, it is important to develop indigenous diagnostics and vaccines. In the past few years, various molecular and immunological techniques have become popular due to their sensitivity & specificity globally. However, those are yet to become popular in all segments of diagnosticians of developing country for diagnosis of diseases in livestock, pet and poultry. The present book is designed to provide minimum basic information including latest theoretical data on some basic immunological and molecular techniques used for diagnosis of bacterial diseases in animals.