Overactive bladder (OAB) is not rarely observed clinical entity affecting lower urinary tract. The OAB pathogenesis is still poorly understood. Two main pathophysiological concepts are postulated: neurogenic theory and miogenic one. The aim of the study was to estimate autonomic nervous system activity by heart rate variability (HRV) assessment in two experimental models: with acute overactive bladder (AOAB) and chronic overactive bladder (COAB) comparing to control. MATERIAL AND METHODS: Study was performed in three groups: control one (10 rats), group with AOAB evoked by i.p. administration of cyclophosphamide (200 mg/kg body weight) (20 rats) and in COAB group caused by 4-times i.p. administration of cyclophosphamide (75 mg/kg body weight). In each case, after urethane anesthesia (1,2 g/kg body weight), 20-minutes ECG recordings were performed with subsequent HRV analysis. Standard time- and spectral (frequency) domain analysis parameters were calculated. RESULTS: Most of differences in time domain analysis parameters were insignificant, except those concerning SDNN and rMSSD. In frequency analysis, a power decrease of all standard spectral components was revealed in both OAB groups, comparing to control. In AOAB, TP and VLF power diminishing were markedly noticed, while COAB group were mostly characterized by LF and HF decrease. In all groups, there were no differences in standardized spectral compounds (nLF, nHF) values. CONCLUSIONS: ANS disturbances, found as standard spectral parameters abnormalities, were demonstrated in both AOAB and COAB. Moreover, the findings of statistically significant differences lack in normalized nLF and nHF powers suggest that VLF changes play essential meaning, reflecting the bladder inflammatory changes progression. Further studies defining precisely ANS disturbances and their reflection in HRV in OAB are required.