Although barnacle larvae have been used in numerous classical studies on phototaxis and spectral response, results have been predominantly qualitative in nature. In this study, short-term phototaxis (direction) and orthophotokinensis (velocity) of Balanus improvisus nauplii are investigated using a new method of video-computer quantification which greatly facilitates studies of movement in small organisms. The ability to rapidly quantify and compare movement parameters makes this system a potentially powerful tool for behavioral bioassays. Thus, this study demonstrates the capabilities of this system and provides a rigorous analysis of the photobiology of barnacle larvae.