Acne vulgaris is a highly prevalent, chronic inflammatory disease of pilosebaceous units. It is the most common skin disease affecting more than 85% of teenagers and young adults. It is not known how often these affected individuals would seek medical advice and treatment, but studies have shown that their quality of life can be severely compromised. The pathophysiology of acne involves increased production of sebum, proliferation of Propionibacterium acnes with resultant increase in chemotactic factors and pro-inflammatory mediators which lead to inflammation, release of lipids into the sebaceous duct and follicle, and obstruction of the pilosebaceous canal caused by hyperproliferation and shedding of keratinocytes in clumps. Hormonal and genetic factors also play major roles. This book offers information pertinent to this widespread condition.