Studies conducted in the past two years have yielded several new insights about neuroendocrine regulation of social recognition. The social recognition deficits seen in oxytocin knockout mice have now been demonstrated in both males and females, as well as in female estrogen receptor knockout mice. The male vasopressin V1A receptor knockout mouse (but not V1B) has a profound social recognition deficit. Preliminary evidence suggests that female V1B receptor knockout mice could also have social memory deficits. Several lines of evidence have emerged that indicate that neuropeptide regulation is significantly modulated by gonadal and corticosteroid activation.