Objectives: this in-vivo study compared the prevalence of Candida spp. in diabetic and non-diabetic patients with/without denture stomatitis (DS). Methods: Edentulous patients (n=210) were selected and divided into three groups: Control group (CG) was formed by 90 individuals without diabetes or DS; Experimental group 1 (EG1) by 80 DS non-diabetic patients; and Experimental group 2 (EG2) by 40 DS diabetic patients. Mucosal characteristics of DS patients were classified in types I, II and III, according to Newton's criteria. Mycological samples were taken from the tissue side of upper dentures for each patient. Samples were cultured in CHROMagar′s plates, which were incubated for 5-days (30°C). Candida spp. were identified by micro-cultivation, hypertonic Sabouraud broth and bioMérieuxID32C assays. A chi-square test for equality of proportions was used to compare the percentage of Candida spp. (P≤.05). Results: C.albicans (Ca) was the predominant species, isolated from 64% (CG), 93% (EG1), and 100% (EG2) of patients. C.tropicalis (Ct) was the second most frequently isolated in EG1 (28%) and EG2 (20%), and its prevalence was significantly higher (P<.01) than in CG (2%). There were no significant differences in the frequency of C.glabrata isolated in CG, EG1 and EG2 (14%, 20% and 10%, respectively). DS patients from EG1 and EG2 demonstrated no significant differences in prevalence of all Candida spp. Considering the 120 DS patients, 25%, 58% and 15% presented with Newton's type I, II and III, respectively, and the frequency distribution of Ct in Newton's type III patients was significantly higher than in type II (P<.05). Conclusion: Ca was by far the most commonly isolated organism. The prevalence of Ct increased in patients with DS and in those with the highest grade of inflammation, suggesting that this species may play an important role in the appearance and development of denture stomatitis. GRANT: FAPESP2006/02842-5; CNPq470337/2007-9.