QtracW is a flexible, stimulus response data acquisition program with averaging and threshold tracking facilities, for studies of human nerves in vivo and animal in vivo/in vitro preparations. It is best suited to situations when the excitability or response varies slowly with time, either due to changes in the stimulus parameters or to an externally initiated treatment, and the data of primary interest are the changes in selected parameters (threshold, amplitude, latency, etc.) of the response with time. Response waveforms can also be recorded, enabling the time course of additional response parameters to be calculated after the recording is finished. QtracW comprises separate stimulation and plotting programs, QtracS and QtracP. QtracW is a multi-channel program, in which the 'channels' (up to 16) may be associated with different physical inputs and outputs, or with different stimulation parameters or different operations on the response waveform. Flexibility comes from the ability to associate any combination of physical or operational parameters with any channel.