Miniature oxygen electrodes functionalized with the yeast Trichosporon cutaneum were used for investigating the relationship between the steady-state method and the dynamic transient method in a batch type BOD sensing system. The two methods are equivalent in terms of reliability, having a high correlation (r2=-0.998) for both standard solutions and wastewater samples. The minimum dI/dt value was used as the response of the BOD sensors in the dynamic transient method. The advantage of this method is that the measuring time can be restricted to about 3 min. The next sample can be injected as soon as the slope of the current/time curve becomes constant, whereas the basic requirement for steady-state measuring is that the current itself becomes constant. This dramatically shortens the interval between each measurement. The stability of the BOD sensors was ensured by injecting a controlled amount of nutrient solution after each measurement. The standard deviation of reproducibility was 7%, not significantly different from that of the steady-state method (8%) but the lower limit of detection for the steady-state method (about 0.5 mg l-1 BOD) is half that of the dynamic transient method.