A computer-assisted retention prediction system (RPS) of fifteen O-ethyl O-aryl N-iso-propyl phosphoramidothioates (1) in reversed-phase HPLC was investigated. The system is based onthe use of four physicochemical parameters (hydrophobicity, electric effect σ, field effect F and stericeffect) which is closely related to the retention mechanism in reversed-phase HPLC. The systemwas evaluated by comparing the measured retention data with the predicted ones. The predictedvalues were consistent with the measured values within a relative error of 11.5%. The computer-assisted retention prediction system (RPS) of fifteen O-ethyl O-aryl N-iso-propyl phosphoramidothioates σ, field effect F and stericeffect) which is closely related to the retention mechanism in reversed phase HPLC. The system is evaluated by comparing the measured retention data with the predicted ones. The predicted values ​​are consistent with the measured values ​​within a relative error of 11.5 %.