Homocysteine has gathered considerable interest in recent years after being implicated in the pathogenesis of various clinical conditions. It has been an elusive target with many conflicting studies casting some confusion over its significance, and much more needs to be done to ascertain its pathophysiological role--especially with respect to regimes aimed at lowering its plasma concentration. Central to this is the development of robust analytical strategies for its determination. This review summarizes the clinical relevance of homocysteine as a diagnostic marker of disease and explores and critically assesses the detection methods that have been developed.