Gender Diagnosticity questionnaires are created by determining which questions best predict membership in gender groups. The UBC Gender Diagnosticity Questionnaire was both created by and administered to a single group of 60 students (50 female, 10 male) enrolled in an undergraduate personality psychology course. Each student was instructed to contribute questions that they believed would differentiate between genders, resulting in a 390-item questionnaire completed by the class. Results mirror other gender diagnosticity studies demonstrating that occupation, hobbies, and activity preferences predicted gender groups with large effects. The final 23-item questionnaire covered a greater range of questions, including sexual preferences, emotional responses, and concern for appearance. Results indicated the questionnaire had good reliability and factorial validity. The only Big Five personality trait that demonstrated a significant correlation with the questionnaire was agreeableness (-.34). This is consistent with past research that Gender Diagnosticity is mostly independent of the Big Five traits.