OBJECTIVE: This study aimed to assess the microbiology of dental unit water and municipal water in terms of Legionella species and total bacteria levels. METHODS: The presence of Legionella species was investigated using the culture method, direct fluorescent antibody and polymerase chain reaction techniques in collected dental unit water and municipal water samples from 71 dental offices in Ankara, Turkey. In addition, total bacterial counts were assessed using the culture method. RESULTS: In 27% of the dental unit water samples and in 13% of municipal water samples, the number of colony-forming units (cfu ml(-1)) significantly exceeded acceptable values for high-risk group patients. No Legionella spp. was found in the dental unit water samples. Legionella SG3 was found in only one municipal water sample. CONCLUSION: The dental unit water systems examined in this study did not include Legionella spp., but other bacteria at high numbers were determined. This is a potential threat, especially for elderly people, the medically compromised patients receiving regular dental treatment and the dental clinic staff.