The aim of the present work is to study the occupants' exposure to fine particulate concentrations in ten nightclubs (NCs) in Athens, Greece. Measurements of PM(1) and PM(2.5) were made in the outdoor and indoor environment of each NC. The average indoor PM(1) and PM(2.5) concentrations were found to be 181.77 microg m(-3) and 454.08 microg m(-3) respectively, while the corresponding outdoor values were 11.04 microg m(-3) and 32.19 microg m(-3). Ventilation and resuspension rates were estimated through consecutive numerical experiments with an indoor air quality model and were found to be remarkably lower than the minimum values recommended by national standards. The relative effects of the ventilation and smoking on the occupants' exposures were examined using multiple regression techniques. It was found that given the low ventilation rates, the effect of smoking as well as the occupancy is of the highest importance. Numerical evaluations showed that if the ventilation rates were at the minimum values set by national standards, then the indoor exposures would be reduced at the 70% of the present exposure values.