Laboratory and field research indicates that the relationships between personal control and stress, coping, and adaptational outcomes are more complex than was once assumed. Believing that an event is controllable does not always lead to a reduction in stress or to a positive outcome, and believing that an event is uncontrollable does not always lead to an increase in stress or to a negative outcome. These complex relationships involving control are examined in the context of Lazarus's cognitive theory of stress and coping. The first part of the article elaborates this theory and shows how two forms of control, generalized beliefs about control and situational appraisals of control, fit into the overall model. Situational appraisals of control are explored in this section, including the question, Control over what? which must be addressed in order to explain some of the perplexing findings. The second part of the article draws on the theoretical formulation of stress and coping to examine three important issues: (a) how believing one has control in a stressful transaction can heighten threat, (b) the relationship between control and coping, and (c) pathways through which control can affect the adaptational outcomes of stressful encounters.