Oxidative stress is associated with many chronic diseases. In this review, we look at the role that oxidative stress may play in diabetes and related cardiovascular disease (CVD) and how oxidative damage may be measured in the plasma. Increased production of reactive oxygen species (ROS) has been implicated in the initiation and progression of both of these conditions and it may be that oxidative stress accounts for the unexplained increase in cardiovascular risk observed in diabetes. Plasma measurements are difficult because of the highly reactive nature of these molecules. Several studies have focused on measuring the total antioxidant buffering capacity of plasma or alternatively specific measures of free radical-mediated damage such as F(2)-isoprostane or oxidised-LDL (Ox-LDL). Perhaps, in the future, the discovery of an 'easy to measure marker' of oxidative stress might be incorporated into risk prediction in diabetes and cardiovascular disease.