We will start with a gener al introduction to t he eld of optical bers in Section 15.2, providing an overview on the di erent light guiding mechanisms and properties as well as on common fabrication techniques. In Section 15.3 the basic concepts and criteria for opto uidic sensing with microstructured bers a re presented, while Section 15.4 covers i mportant i ssues concerning t he i njection a nd ow of liquids in these bers. e current state of the art of ber-based sensing is then reviewed in Sections 15.5 through 15.7, discussing the advantages and drawbacks of various ber designs and sensing methods. As a s lightly di erent application, t he c oncept of l ight-induced pa rticle t ransport i nside m icrostructured bers is introduced in Section 15.8, reviewing also some of the recent experiments. Finally, a brief summary and discussion on the current challenges and prospects of biochemical sensing with optical bers is given in Section 15.9.