KEY WORDS: (STRESSORS, JOB STRESS & STRAIN, DEMANDS-CONTROL- SUPPORT MODEL) Most of the stress theories were developed to describe reactions to “inevitable” acute stress in a work environment threatening the individual organic survival. However, the demand-control-support model (DCSM) was constructed for work environments where “stressors” are persistent, not initially life threatening, and are the products of complicated human organizational decision making process. Here, the controllability of these stressors is very important, and becomes more important as we develop ever more complex and integrated organizational system, with ever more complex personality traits of individual behavior. The DCSM (Karasek 1976 & 1979; Karasek and Theorell 1990) is based on psychosocial and physical characteristics of work environment: the psychological and physical demands of work and a combined measure of task control through personal skills (decision latitude) and social support. Job control includes the worker’s abilities and skills for coping with demands and the latitude to decide how a specific task should be accomplished. Job stress depends on the level of demands, on the worker’s decision- making latitude, and on the quality of social support available from management and co-workers. The models predict, first, stress-related strain indices, and, secondly, active/passive behavioral correlates of jobs. These models propose that worker strain and active learning are determined by particular combinations of job demands, job control and social support at workplace. Specifically, incumbents of jobs that are high in demands, low in control, and low in support are expected to show high levels of strain, whilst incumbents of jobs that are high in all three job factors are expected to display high levels of activity, learning and participation, both on and off the job. The models also propose that prolonged exposure to combinations of these job conditions influence workers'' immediate indices (job anxiety, job dissatisfaction and somatic symptoms) and remote indices (mastery, neuroticism, and employee’s turnover intention and activity participation) of job strain. This thesis reports an attempt to clarify, critically evaluate, extend and test Karasek & Theorell’s models. Self-report data, as well as information obtained from Distribution Companies (DISCOs) of power wing of Water and Power Development Authority (WAPDA) are used to assess the independent linear, quadratic, additive and interactive effects of job factors. Study 1 is being conducted a cross-sectional design, and self-report measures of job demands, job control and job stressors to predict several indices of worker strain and performance. Study 2 was designed to ensure the authenticity of study 1 and thus to provide a more valid and logical proof of test of Karasek’s hypothesis and models. Personality variables of employees (neuroticism, mastery) were also determined to predict the relationship with job factors and indices of job strain. In general, the results from this research confirm past findings regarding the effects of job demands, control and social support on strain. The research makes several important contributions to practical implications to job development and jobs re-design. More practically, the research reinforces the importance of providing "control-enhancing" opportunities for employees who are facing problems to highly demanding jobs. Because the cost of stress and strain is very high for individuals (poor health, accidents, job dissatisfaction, health care expenditures), for companies or organizations (poor performance, lack of productivity, effects the quality of work, spoilage and defective work, absenteeism, medical costs, turnover, even labor conflicts and strikes), and for society (health care costs, loss of intellectual capital, low-level performance and economic competitiveness). Recommendations for future research include the need to test an expanded model using multi-wave cross-sectional designs and magnitude of multi-stressors of work environment.