A group of full-denture-wearing patients with erythematous candidiasis was matched by age and sex with a group of healthy, full-denture-wearing persons who served as controls. In the group with erythematous candidiasis, clinical symptoms and signs of the disease were recorded. Denture hygiene and tobacco use were noted in both groups. Epithelial smears and imprint cultures were obtained from both groups from specified sites. Cultures were grown and subjected to species identification and C. albicans strain differentiation by a morphotyping technique. Denture-wearing subjects who smoked tobacco had a significantly greater incidence of erythematous candidiasis than the controls. Five species of Candida were isolated from both groups, with C. albicans as the dominant species. Twenty different morphotypes of C. albicans as well as strains involved in erythematous candidiasis were also isolated from the oral cavities of healthy, full-denture-wearing control subjects.