The second edition of this book deals with theoretical foundation and principles of design of mixed-flow pumps and fans. There is a detailed discussion and information of the principles of design which shows an increasingly wider application. New methods of impeller design are included and to date literature was covered. Modern theories of cavitation concepts are introduction to complete method of calculating developed cavitation. A major application of bleeding system is given illustrating useful utilization to overcome cavitation during pumping process. It also gives information on pump design and the effect of blade setting angle has on cavitation calculation of Fan characteristics its ways of regulation/control, Fan group operation with means to avoid problems on blade erosion and fan noise conclude this edition. This book is offered to students, engineers and their associates who are concerned with the construction and use of mixed-flow pumps/fans. The book can be used as a reference in mechanical faculties and research institutions. It can also fit as supplementary courses for young engineers working as pump/fan designers. Pump/Fan manufacturers will find it very useful.