Purpose: The aim of this study was to explore the effects of A-solution on halitosis and oral status in preoperative NPO patients. Methods: A nonequivalent control group, non-synchronized pretest-posttest design was used in this study. The participants in this study were 66 patients who were admitted for gynecologic surgery. The experimental treatment was to give oral gargling with A-solution, blended essential oils and diluted with distilled water. To identify the experimental treatment effects, halitosis, salivary pH, and oral status were measured by a portable halitosis detector, visual analogue scale, Bromo Thymol Blue (BTB), Bromo Cresol Purple (BCP) test paper and oral assessment guide. Data were analyzed using X²-test, t-test with PASW 18.0 version. Results: Participants were homogeneous before experimental treatment. Objective halitosis in the experimental group, measured by a portable halitosis detector (t= -8.34, p<.001) was significantly lower than the control group. Subjective halitosis was significantly lower in the experimental group (t= -9.29, p<.001). Salivary pH was significantly different between two groups (t=8.81, p<.001). Oral status was significantly better in the experimental group (t= -13.31, p<.001). Conclusion: These findings indicate that oral gargling using A-solution is effective in reducing patient halitosis, and improving oral status.