p16INK4a (p16) tumor-suppressor protein is a biomarker of human papillomavirus (HPV) oncogenic activity that has revealed a high rate of positivity in histological high-gade squamous intraepithelial lesion/cervical intraepithelial neoplasia grade 2 (HSIL/CIN2) lesions. However, there is a paucity of data regarding p16 status as a surrogate marker of HSIL/CIN2 evolution. The aim of this study was to evaluate the outcome of HSIL/CIN2 patients followed up without treatment for 12 months according to p16 immunohistochemical staining. Patients diagnosed with HSIL/CIN2 colposcopy-directed biopsy, were recruited prospectively between December 2011 and October 2013. p16 staining was performed in all HSIL/CIN2 diagnostic biopsies. Follow-up was conducted every 4 months by cytology, colposcopy and biopsy if suspicion of progression and once the 12 months of follow-up completed. Complete regression, partial regression, persistence, and progression rates of HSIL/CIN2 were defined as a final outcome. A total of 96 patients were included in the analysis. The rate of spontaneous regression was 64%, while 28% had persistent disease, and 8% progressed at 12 months of follow-up. p16 was positive in 81 (84%) initial HSIL/CIN2 biopsies. Regression was observed in all 15 p16 negative cases and in 46 of 81 (57%) p16 positive cases (P=0.001). In conclusion, patients with p16 negative HSIL/CIN2 biopsy had a high rate of regression during first 12 months of follow-up. Status of p16 staining could be considered for HSIL/CIN2 management.