Regurgitant jets were simulated in vitro and analysed using Doppler colour flow imaging. The regurgitant volumes were estimated using total jet area (JA), variance area (VA), and the maximum area of variance x time to maximum area of variance (MAVT). Both flow rate and injected volume were significantly correlated to area of variance (r = 0.89 and r = 0.98, respectively) for a given orifice size. When MAVT was analysed, it correlated better to injected volume (r = 0.97) at a fixed flow rate, than varying flow rate (r = 0.69) at a fixed injected volume. The relationship between MAVT and injected volume was also examined with varying flow rate. There was a highly significant correlation between MAVT and injected volume under these circumstances (r = 0.99). A similar relationship between MAVT and injected volume was found when the orifice size was altered. Using multivariate regression analysis the injected volume was best defined by MAVT (R2 = 0.88). The addition of orifice size only improved the fit to the model marginally (R2 = 0.90). These data document the importance of analysing the time to maximum area of variance when applying Doppler colour flow imaging to regurgitant jets. MAVT is a better predictor of regurgitant volumes in vitro compared with jet sizes alone and may have potential use in man to quantify the severity of regurgitant valve lesions.