We present in this communication an algorithm that offers continuous, on-line, real-time analysis of the power spectrum (CORAPS) of systemic arterial pressure (SAP) signals. Based on direct fast Fourier transform of raw SAP signals into power spectral density, it is suitable for the delineation of acute SAP spectral changes over time after physiological or pharmacological perturbations. Thus it is an improvement over most current methods, which only generate the spectra off-line or from intermittent data. Furthermore, all executions can be accomplished economically with a general-purpose personal computer. We demonstrated and quantified vivid sequential alterations in the low-frequency components (< 3 Hz) of the SAP spectrum, which purportedly reflect the influence of vasomotor, baroreceptor, and respiratory activity on SAP during pentobarbital administration or transient hypertension. Three window options incorporated into the algorithm further improved the frequency or temporal resolution and discrimination of the spectral changes during abrupt hypertension or hypotension. Thus our CORAPS algorithm may be useful as an on-line monitor for acute hemodynamic changes.