The inbred strain FVB/N is becoming increasingly popular to generate transgenic animals. We compared animals from this strain with well-characterized C57BL/6J animals on four different behavioral tests: the elevated plus maze test of anxiety, a standard opponent aggression test, the open-field test, and spatial learning in a radial maze. Our results indicate that FVB/N animals have slightly higher levels of anxiety and aggression, are hyperactive, and have a clear learning deficit. The latter finding seems to be related to an exceptionally small intrapyramidal and infrapyramidal mossy fiber projection. It is recommended that transgenic experiments employing this strain use F1 crosses between FVB/N and C57BL/6J as much as possible for behavioral experiments intended to evaluate spatial learning.