Purpose: This study assessed the effectiveness of three antimicrobial mouthrinses in reducing microbial growth on photostimulable phosphor (PSP) plates. Materials and Methods: Prior to performing a full-mouth radiographic survey (FMX), subjects were asked to rinse with one of the three test rinses ($Listerine^{(R)}$, $Decapinol^{(R)}$, or chlorhexidine oral rinse 0.12%) or to refrain from rinsing. Four PSP plates were sampled from each FMX through collection into sterile containers upon exiting the scanner. Flame-sterilized forceps were used to transfer the PSP plates onto blood agar plates (5% sheep blood agar). The blood agar plates were incubated at $37^{circ}C$ for up to 72 h. An environmental control blood agar plate was incubated with each batch. Additionally, for control, 25 gas-sterilized PSP plates were plated onto blood agar and analyzed. Results: The mean number of bacterial colonies per plate was the lowest in the chlorhexidine group, followed by the Decapinol, Listerine, and the no rinse negative control groups. Only the chlorhexidine and Listerine groups were significantly different (p=0.005). No growth was observed for the 25 gas-sterilized control plates or the environmental control blood agar plates. Conclusion: The mean number of bacterial colonies was the lowest in the chlorhexidine group, followed by the Decapinol, Listerine, and the no rinse groups. Nonetheless, a statistically significant difference was found only in the case of Listerine. Additional research is needed to test whether a higher concentration (0.2%) or longer exposure period (two consecutive 30 s rinse periods) would be helpful in reducing PSP plate contamination further with chlorhexidine.