OBJECTIVE: To compare the frequency of p16- and Ki-67-positive cells on immunohistostaining among women with progression, persistence, or regression of cervical intraepithelial neoplasia grade 2 (CIN2). METHODS: A retrospective study was conducted of women with CIN2 diagnosed by histology who were treated at a university hospital in Japan during 2004-2011. The immunostaining patterns for p16 and Ki-67 were analyzed and compared between patients with disease progression, persistence, or regression. Kaplan-Meier analysis was used to evaluate the progression rates stratified by immunostaining, and multivariate analysis of risk factors for progression was performed using the Cox proportional hazards model. RESULTS: The analysis included 59 women with progression, 35 women with persistence, and 28 women with regression. Deep p16 expression (staining in more than half of the cervical intraepithelial compartment) and positive Ki-67 staining in more than 50% of cells were significantly more common among women with progression than among those with regression. The risk factors for progression of CIN2 were deep p16 expression (P<0.001) and a Ki-67 ratio of more than 50% (P<0.001). CONCLUSION: Among women with CIN2, positive immunohistostaining for p16 and Ki-67 was strongly associated with disease progression.