This book is intended a guide to student and as a manual for Engineers, Architect, Builder, etc. engaged in the practical of mechanical and Electrical Services in buildings. The book was divided into six chapters covering the study of building services and this was arranged so that it can be worked through progressively from the beginning to the end. Chapter one described the background of the subject which gives the essential requirement of human existence. Chapter two is relatively concern with the environmental systems together with the design of plumbing systems and drainage installations. Chapter three deals with the ventilation system in the building and this also covered the purpose and the method of ventilation. Chapter four present the lighting system, sources of light and the lighting conditions were discussed. Electrical installation in the building was presented in chapter five. Chapter six illustrates the cooling system in a building. Couple with all this, the book contains worked examples. The author will be glad to receive comments, corrections and suggestions from the users of this book.