The University requires that students in the Ph.D. programs take comprehensive exams during the last semester of coursework. Students register for comprehensive exams during the Catholic University identified registration period.
(Doctoral Comps with classes)
(Doctoral Comps without [any registered] classes)
Students should register for the Comprehensive Examination before the start of classes and must be registered before the conclusion of the Registration Drop/Add Period for the semester in which they plan to take the examination. Upon approval of the student's credentials by the school dean and, where appropriate, the department chair, the student will be granted written permission by the school dean to take the Comprehensive Examination. The student may not sit for the examination until he or she has received this permission.
The Comprehensive Examination is marked pass or fail. If the student fails the examination, he or she may retake the examination only once. Depending on school and department (where applicable) policy, the student must retake either the entire examination or just the failed portion. A student who fails the Comprehensive Examination twice may not be considered for admission to candidacy for the doctoral degree. A second failing grade is noted on the student's permanent records.
From Academic Regulations for Doctoral Degrees: http://policies.cua.edu/academicgrad/doctoralfull.cfm
Admission to Candidacy
Students are not considered to be doctoral candidates until after successful completion of the comprehensive exam. The data of candidacy is important as that is when the time limit begins for completion of the DNP project. Please reference the policy below from the Graduate Handbook. From the date of candidacy, the student has 5 years (10 semesters) in which to complete the project.
Admission to a doctoral program does not automatically include admission to candidacy for the doctoral degree. The faculty of the school and department (where applicable) must evaluate the progress of the student and determine that the student has completed all course and other requirements, has passed the Comprehensive Examination and is otherwise qualified to fulfill the requirements of the doctoral dissertation or its equivalent. Schools and departments (where applicable) may follow different procedures for formal admission to candidacy. The student should consult with the school dean or department chair (where applicable) for information on these procedures.
The student’s school or department (where applicable) may record the actual date of the successful vote for candidacy. However, candidacy for the doctoral degree begins formally and administratively on the first day of the semester following successful completion of the Comprehensive Examination. The student has five (5) years (i.e., ten  semesters) from this date of formal, administrative admission to candidacy to complete, defend and deposit the dissertation. Individual schools and departments may, at their discretion, set different time limits for completion, as long as these do not exceed the five (5) year (ten  semester) limit. If more than five (5) years, or the time set by the schools or departments, elapse between formal admission to candidacy and oral defense of the dissertation, the doctoral candidate may be required to retake the Comprehensive Examination or fulfill additional requirements as determined by the school and department.