Actinic cheilitis is a potentially malignant lesion most commonly found in the lower lip of individuals with chronic exposure to ultraviolet radiation. The aim of this study was to develop and to test a clinical index that can be used to assess the severity of actinic cheilitis. The clinical index of actinic cheilitis was applied to 36 patients. An incisional biopsy was obtained to grade oral epithelial dysplasias following the World Health Organization (WHO) and binary systems, and to evaluate their association with clinical characteristics by Fisher?s exact test (P<0.05). The accuracy of the index was evaluated based on sensitivity, specificity, positive and negative predictive values, and receiver operating curve. The blurring between the border of the lip and the skin was significantly associated with cases without dysplasia/mild epithelial dysplasia (P=0.041) and with low risk of malignancy (P=0.005). Ulcers and crusts were significantly associated with moderate/severe epithelial dysplasia (P=0.002 and P=0.012, respectively) and high risk of malignancy (P=0.005 and P=0.045, respectively). Erosion showed a significant association only with high-risk cases of malignancy (P=0.024). The cut-off values of the diagnostic test showing the best performance were 10 for the WHO grading system and 11 for the binary system. The index cut-offs with the highest accuracy were considered indicators for a biopsy. Erosion, ulceration and crusts were associated with more severe oral epithelial dysplasias.