The family of peptides designated as cathelicidins was identified over a decade ago. Cathelicidins have since gained increasing recognition, both as endogenous antibiotics and as effector molecules of the innate immune system. The human cathelicidin LL-37 is widely expressed in human tissues and plays diverse biological roles. It contributes substantially to host defense and impacts multiple aspects of immunity. In view of the escalating importance of cathelicidins, the activities of LL-37 with an emphasis on antimicrobial, immunomodulatory, anti-inflammatory, angiogenic, anticancer and procancer effects are discussed in this review article.