One component of host defence at mucosal surfaces are epithelial-derived antimicrobial peptides. Cathelicidins are one family of antimicrobial peptides characterized by conserved pro-peptide sequences that have been identified in several mammalian species. LL-37/hCAP-18 is the only cathelicidin found in humans and is expressed in inflammatory and epithelial cells. Besides their direct antimicrobial function, cathelicidins have multiple roles as mediators of inflammation influencing diverse processes such as cell proliferation and migration, immune modulation, wound healing, angiogenesis and the release of cytokines and histamine. Finally, cathelicidin antimicrobial peptides qualify as prototypes of innovative drugs that may be used to treat infection and/or modulate the immune response. This review provides an overview of antimicrobial peptides of the cathelicidin family, the structures of their genes and peptides and their biological functions.