Polylactic acid (PLA) is a synthetic and biodegradable polymer. PLA can have important applications in tissue engineering as three-dimensional porous structures. Biodegradable polymers are used in medicine to replace and increase the volume of tissues, as tissue supports and also for controlled drug release. One of the most widely used biodegradable polymers is polylactic acid (PLA), as it is easily biodegraded. This material is used as microspheres or microcapsules to host a broad diversity of drugs, such as antiinflamatory, anticonceptives, narcotics antagonists, local anesthetics and vaccines. This book discusses new developments in the research of polylactic acid.