The in vitro effects of phenylephrine solution on ciliary beat frequency (CBF) in terms of different concentrations and exposure times were investigated using a video-computerized analysis technique. Nasal epithelial cells were taken from inferior turbinate of 10 volunteers by scraping the nasal mucosa with a cytology brush. CBF was measured in five different concentrations including 0.125%, 0.25%, 0.5%, 1%, and 2.5%. Each specimen was incubated in different solution for 6 days and CBF was measured at 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, 12 hours, 1 day, 2 days, 3 days, 4 days, 5 days, and 6 days. CBF decreased significantly after 12-hour incubation in 0.125% phenylephrine solution and after 8-hour incubation in 0.25% phenylephrine solution, both clinically used concentrations. There were significant decreases in CBF after incubation in 0.5% phenylephrine for 2 hours, in 1% for 1 hour, and in 2.5% for 30 minutes (P < 0.05, repeated measure analysis of variance [ANOVA]). CBF of the nasal respiratory ciliated cells significantly decreased with increasing concentrations of phenylephrine solution and with increasing incubation times at the same concentration (P < 0.05, repeated measure ANOVA). The results of this study suggest that phenylephrine may inhibit ciliary beat in vitro by its pharmacological effect at lower concentrations than clinically used ones.