Infrared spectroscopy has proved to be a powerful tool for the study of biological molecules and the application of this technique to biological problems is continually expanding, particularly with the advent of increasingly sophisticated sampling techniques associated with Fourier transform infrared spectroscopy in recent decades. Biological systems, including lipids, proteins, peptides, biomembranes, nucleic acids, animal tissue, microbial cells, and clinical samples, have all been successfully studied using infrared spectroscopy. Infrared spectroscopy has been employed for a number of decades for the characterization of isolated biological molecules, particularly proteins and lipids. However, the last decade has seen a rapid rise in the number of studies of more complex systems, such as diseased tissues. Microscopic techniques combined with sophisticated analytical methods allow for complex samples of micron size to be investigated. A review of the sampling methods used for biological molecules is provided here. Examples of how infrared spectroscopy may be applied to various biological fields are also provided. Keywords: Attenuated Total Reflectance Spectroscopy; Diffuse Reflectance Spectroscopy; Fourier Transform Infrared Spectroscopy; Group Frequencies; Infrared Mapping; Mid-infrared; Near-infrared