The performance effect is used to explain the significant differences between salespersons’ self-evaluation and supervisors’ ratings of job performance. It is shown that bottom performers overestimate, whereas top salespeople underestimate their performance. Also, results indicate that bottom performers are significantly more inaccurate than top salespeople in their job performance estimation. Finally, results indicate that the relationship between inaccuracy of self-evaluation and job performance is curvilinear. Managerial implications are provided as well as directions for future research and limitations.