The psychological and social experiences people have in the workplace, often referred to as the psychosocial work environment, have become an important component in studies related to stress and occupational health. Among the theories of stress there are a set of models that focus specifically on the effects of psychosocial work environment factors on mental strain and physical illness. These are sometimes identified as models of the psychosocial work environment. The two most commonly used models to study the relationships between the psychosocial work environment and health are the demand-control model and the effort-reward imbalance model. In a broad sense the demand–control model holds that the demands workers experience at the point of production interact with the opportunities they have to influence work tasks and procedures to create different levels of stress. High job demands, in the form of high workloads and intense time pressure, coupled with lack of control are likely to lead to mental strain and cardiovascular disease, particularly when social support is low. The effort-reward imbalance model on the other hand identifies the imbalance employees experience between high work effort and low rewards, lack of promotional opportunities, and job insecurity as important sources of stress and other negative health effects. To date these two quite similar models have been used in most of the European countries and America. However, few studies have been conducted so far in some countries of the Asian region. In this regard, this chapter highlights the theory and evidence behind the development of these two models, particularly, the demand-control model and how they measure the impact of psychosocial work-environments on health, in various countries around the world.