A spatiotemporal filtering method for single-trial ERP component estimation is presented. Instead of modeling the entire ERP waveform, the method focuses on the ERP component local descriptors (amplitude and latency) thru the spatial diversity of multichannel recordings and thus it is tailored to extract signals in negative signal to noise ratio conditions. The model allows for both amplitude and latency variability in the ERP component under investigation. We applied the method to the estimation of the P300 component in an oddball target detection task and found that negative correlations exist between response time and single-trial P300 amplitude.