EthoLog is a tool that aids in the transcription and timing of behavior observation sessions--experimental or naturalistic, from video/audio tapes or registering real time. It was created with Visual Basic and runs on Windows (3.x/9x). The user types the key codes for the predefined behavioral categories, and EthoLog registers their sequence and timing and saves the resulting data in ASCII output files. A sequential analysis matrix can be generated from the sequential data. The output files may be edited, converted to plain text files for printing, or exported to a spreadsheet program, such as MS Excel, for further analyses.