This chapter discusses hollow fiber liquid-phase microextraction (LPME). The chapter comprises a short discussion of the basic setup and principles for LPME, and the historical development. The theory of LPME is also discussed including equations for extraction recoveries and extraction kinetics. This theory is the basis for method optimization, which is covered comprehensively in a forthcoming section. Different applications of LPME are also discussed, with special emphasis on environmental and pharmaceutical analysis. Most attention is focused on recent applications in which LPME has been combined with either gas chromatography-mass spectrometry or high-performance liquid chromatography-mass spectrometry (LC-MS). This chapter also presents a comprehensive discussion of the performance of LPME. Electromembrane extraction, which is a new type of LPME utilizing electrical fields for extraction, is also mentioned. Future perspectives are also discussed. The chapter contains 105 references to original research papers on LPME.