Withanolides are a group of naturally occurring C28 steroids built on an ergostane skeleton functionalized at carbons 1, 22 and 26, commonly known as the withanolide skeleton. Over the period of August 1996 to March 2010, 360 new naturally occurring withanolides were isolated and identified. This review provides a comprehensive summary of the structural classification and distribution of these new compounds. The diverse biological and pharmacological activities of natural withanolides are also discussed based on their structural features. A total of 211 references are cited in this review.