We investigate the possibility of using ALA-derived PpIX fluorescence spectroscopy for the detection of epithelial hyperkeratosis (EH) or epithelial dysplasia (ED) lesions in oral submucous fibrosis (OSF) patients that could not be found by autofluorescence spectroscopy. Twenty percent of ALA solution gel was applied onto oral neoplasia and surrounding normal tissue [normal oral mucosa (NOM)] for . Fluorescence emission spectra were measured under excitation. Generally, the most intense fluorescence emission peaks occurred at 460 and . The ratios of the area under red peak to the area under blue peak ), denoted as , were calculated. We found that OSF mucosa has the lowest value, followed by NOM, EH on OSF, and ED on OSF. An ANOVA test showed significant differences between OSF, NOM, EH on OSF, and ED on OSF . However, measurements of autofluorescence (i.e., before ALA application) show no significant differences between OSF, NOM, EH on OSF, and ED on OSF (ANOVA test, ). These results indicate that ALA-induced PpIX fluorescence spectroscopy could be used to identify the premalignant lesions on oral fibrotic mucosa, which could not be found by autofluorescence.