The potential for behavioral tests in a pollutant effects aquatic monitoring program is discussed. Various types of individual and inter-individual behavioral responses are noted, but emphasis is placed on individual behaviors since they are of a less complex nature and may be easier to use routinely. Measurement of undirected (nonsimulated) locomotor activity may provide an index of neuromotor function. Locomotor responses to specific external stimuli may also be utilized to test specific motor and sensory capacities. Locomotor activity has been employed extensively in mammalian behaviorial toxicology, this parameter may also be valuable with aquatic organisms. This paper reviews past and some current research on the effects of pollutants on the locomotion in aquatic organisms, examining in some detail undirected activity, photoresponses, thermal regulatory responses and rheotaxis. Several criteria are cited to evaluate behavioral tests for monitoring purposes and some research needs in this area are enumerated.