The recent flurry of attention to burnout syndrome still leaves numerous questions unanswered. One of them is the relationship between individual factors and the development of burnout. An understanding of the individual factors underlying burnout must include an assessment of the individual reactivity to stress. The occurrence, distribution and relationship with stress reactivity of the three dimensions of the burnout syndrome (emotional exhaustion, depersonalization and lowered feelings of personal accomplishment) were studied among a representative sample of the different professionals involved in the Primary Care Health System. Our results indicate that stress reactivity could be a variable that modulates the experienced psychopathology, suggesting a predisposition that increases the susceptibility to the development of burnout.