Longchen Rabjam is revered as one of the greatest masters in the Nyingma school of Vajrayana Buddhism. He wrote more than 250 treatises on a wide variety of topics, but is best known for his works on dzogchen, or great perfection, especially the extensive scholastic exegesis of the great perefection tantras known as The Seven Treatises. This collection discusses the promordial nature that is the ground of all experience, the view, meditation and conduct of the spiritual path, and the final freedom that is the fruition of the path. The treasury commonly known as the Choying Dzod consists of two texts, Longchen Rabjam's source verses and his own commentary on them (published individually as A Treasure Trove of Scriptural Transmission). The present volume, The Precious Treasury of the Basic Space of Phenomena, contains a poetic summary of the subject matter dealt with at length in the commentary.