DBA/2J and C57BL/6J mice were injected with nicotine, and tested in a Y water maze in two procedures: the L procedure, coresponding to innate behavior, in which the animals must swim towards the light, and the D procedure, corresponding to the acquisition of a new pattern of behavior, in which they must swim toward the dark. Three sets of experiments were carried out: 1. In the pre-trial experiments, nicotine administration improved the innate tendencies of both strains, while the acquisition of a new behavior was facilitated in the C57 and impaired in the DBA mice. 2. In the post-trial experiments (D procedure), nicotine administration induced clear facilitating effects on the consolidation processes of the C57, while impairing these processes in the DBA strain. 3. The only effect evident, following nicotine administration, before the highest doses were reached, in the trained mice of both strains, was a performance impairment of the DBA mice trained in the L procedure.