Cystometry, employing natural or pump-induced bladder filling, is the most widely used method for studying bladder reflexes and micturition in conscious rats. However, discrepancies in basal values of urodynamic parameters are often reported, especially for micturition pressure. The aim of this study was to establish whether the type of pump used (peristaltic or infusion) might yield different urodynamic parameters. Differences between natural filling (evaluated in water-loaded animals and considered "physiological micturition") and pump-evoked cystometrograms, as well as the compliance of these systems, and the effects of pharmacologically diverse drugs (prazosin, oxybutynin, and naproxen) acting on the bladder voiding were evaluated. Micturition pressure recorded from pump-evoked cystometrograms showed differences from natural micturition that were related to the total compliance of the system (pump + tube) and not only to the nature of the pump used. Drug-induced changes of micturition pressure during natural micturition resembled those recorded during bladder infusion with a peristaltic pump more than those with an infusion pump. Other basal values and drug-induced changes of bladder capacity were the same during natural and pump-evoked micturition. The present findings indicate that cystometrographic parameters obtained during pump-evoked micturition with a system at high compliance (peristaltic pump) are equivalent to those observed during physiological micturition.