The Johari Window--a model that categorizes degree of self-awareness and openness in communication into (1) information known to self and others (open), (2) information known to self but not to others (hidden), (3) information known to others but not self (blind), and (4) information known neither to self nor to others (unknown)--is a frequently used pedagogical and research tool. To test its reliability and validity, 61 male and 99 female undergraduates from basic communication courses were classified as either open or hidden, based on their responses to the Johari Window, and were then administered reliable and valid measures of self-esteem and communication anxiety. Although it had been reasoned that people seeing themselves as more open would have higher levels of self-esteem, results of these measures showed no significant differences between the hidden and open groups, indicating that the Johari Window does not predictably relate to any of the tested measures. The lack of significant findings may be due, in part, to the Window's failure to distinguish between appropriate and inappropriate self-disclosure. Though apparently not a useful research tool, the model still can be an important pedagogical device if it is accompanied by necessary qualifications. (MM)