This research develops and tests a model relating complexity of self-representation to affective and evaluative responses. The basic hypothesis is that the less complex a person's cognitive representation of the self, the more extreme will be the person's swings in affect and self-appraisal. Experiment 1 showed that those lower in self-complexity experienced greater swings in affect and self-appraisal following a failure or success experience. Experiment 2 showed that those lower in self-complexity experienced greater variability in affect over a 2-week period. The results are discussed, first, in terms of self-complexity as a buffer against the negative effects of stressful life events, particularly depression; and, second, in terms of the thought patterns of depressed persons. The results reported here suggest that level of self-complexity may provide a promising cognitive marker for vulnerability to depression.