Objective: The loudness dependence of the auditory evoked potential (LDAEP) has been suggested as a potential marker of the functional status of the serotonin system in vivo. While the most convincing evidence for this marker has derived from animal studies or findings in human populations with a presumed serotonin dysfunction, human pharmacological manipulation studies have been less convincing. The current study used the LDAEP to assess serotonergic gender differences in a large sample of healthy human males and females to ascertain whether or not a gender dichotomy can explain the inconsistencies in the literature. Methods: Data from sixty-five healthy participants from four independent studies were pooled and their N1/P2 slopes were quantified. Results: Mean N1/P2 slopes for females were higher than those for males (p < .0001). Conclusion: This finding suggests reduced serotonin function in females as measured using a functional marker that is sensitive to the level of serotonergic neurotransmission. In addition these findings suggest that inconsistencies in the literature may be explained by ceiling effects in healthy male subjects.