Spike Sort 3D is the utility used for on-line and off-line spike waveform classification. Spike Sort 3D is integrated into Cheetah DAS Software and also runs as a stand-alone off-line program, thus it allows seamless movement and a consistent GUI between on-line and off-line spike sorting. It allows users to choose from many options for manual clustering, including convex polygons and rectangular boundaries in feature space, and waveform templates (window discriminator) on raw spike data. Data clusters can also be defined in any arbitrary 3 dimensional view of feature space. Waveform parameter calculations include standard measures such as Peak, Valley, Area and Energy to advanced measures such as Principal Component Analysis. Spike files may be saved with new assignments intact, cluster definitions may be saved for later use, and timestamp files are created for importing clustered data into virtually any analysis software.