The work presented in this thesis was re-submitted to The University of Manchester for the degree of Doctor of Philosophy in July 2011 by Graham Dinsdale and is entitled "Optical Coherence Tomography: applications and developments for imaging in vivo biological tissue".In this thesis the design and build of a high-speed, video-rate optical coherence tomography (OCT) imaging system is described. The system was designed for the purpose of imaging human skin in vivo, particularly that of patients suffering from conditions such as systemic sclerosis. Component selection and design decisions are discussed in the context of the intended final application. Initial test images from the system are presented. In the context of building an OCT system, a supercontinuum light source was characterised and tested for its suitability for use in the OCT environment. Parameters such as coherence length were measured using simple interferometry techniques, while practical considerations such as portability and ease of system integration were also considered.Several applications of OCT imaging techniques were also investigated, using two commercially-available OCT systems from Thorlabs, Inc. A liquid-based skin and blood flow model was constructed using narrow glass capillary tubes, pumped through with scattering solutions of Intralipid or suspensions of polystyrene microspheres. The concentration of the solutions was tuned by dilution in order to best model the scattering parameters of blood. The model also used similar liquid solutions to model static tissue surrounding the blood vessels. Doppler OCT images of the model under various conditions were recorded, and velocity profiles of the flowing liquids were extracted.Using the same commercial OCT systems, imaging over two separate wavelength regions was also performed on the skin of several different species of neo-tropical tree frog, some of which have interesting reflective properties due to the presence of a pigment called pterorhodin. Cross-sectional OCT images of the skin are presented, and averaged depth profiles extracted from them. This is the first time that OCT imaging has been applied to this problem.A clinical study of skin thickening and microvascular function in patients with systemic sclerosis compared to healthy controls was also carried out, again involving a Thorlabs, Inc. commercial OCT system. This study was carried out at Salford Royal Hospital under the supervision of the rheumatology research group. Skin thickness was assessed using OCT and high-frequency ultrasound imaging. Microvascular function was measured using nailfold cappilaroscopy and laser Doppler imaging. Images from the study are presented here.