An experiment was conducted to provide empirical support for the notion that asymmetrical causal attributions for favorable and unfavorable outcomes result from a self-serving attributional bias that occurs independently of self-presentational concerns. Subjects did either well or poorly on an ego-involving test for which their performance, attributions, and evaluations of the test were either public or private. A pattern of self-serving responses for subjects' attributions and evaluations of the test was found in the private conditions, thus providing evidence of the influence of outcome favorability on individuals' perceptions of causality. Theoretical and practical implications of these finding are discussed and suggestions for future research are offered.