The aim of this study was to evaluate saliva as a potential monitoring medium for procainamide (PA) and its metabolite, N-acetylprocainamide (NAPA). Saliva concentrations of PA and NAPA were determined both in single and repeated oral administration of PA in four healthy subjects. PA and NAPA were detected both in serum and saliva after 500 mg of single oral administration of PA. After single oral administration, serum and saliva concentrations of PA and NAPA reached peak levels at about 1 h and declined thereafter. The mean half-lives of PA were 2.35 h in serum and 1.28 h in saliva. The mean half-lives of NAPA were 5.29 h in serum and 5.01 h in saliva. In this study, PA and NAPA concentrations in saliva were nearly twice as high as those in serum upon chronic oral administration as well as those in a single oral dose of PA. Significant correlation coefficients were observed between serum and saliva concentrations of PA (r = 0.78, p < 0.001, n = 21) and NAPA (r = 0.76, p > 0.001, n = 21) in single oral administration of PA. Significant correlation coefficients were also observed between serum and saliva concentrations of PA (r = 0.89, p < 0.001, n = 17) and NAPA (r = 0.87, p > 0.001, n = 19) after repeated oral administration of PA. The saliva-to-serum ratios of PA and NAPA maintained nearly constant at 1 h after oral administration. It would appear from this study that saliva is a suitable medium for monitoring PA and NAPA concentration regarding acetylator status.