We studied the penile erectile response to cavernous nerve electrostimulation in five monkeys and eight dogs before and during spinal anesthesia. Anesthesia was obtained by intradural injection (at L4-L5 level) of either xylocaine (two mg./kg. body weight) or tetracaine (0.2 mg./kg.). In monkeys, systolic blood pressure reduction (average 17.2%), slight elongation and tumescence of the penis, and increase of intracavernous pressure were noted after spinal anesthesia. Electrostimulation of the cavernous nerves resulted in longer erection and detumescence phases than obtained before anesthesia. In dogs, a similar blood pressure decrease (16.6% average) was noted after anesthesia. The response during anesthesia to electrostimulation of the erectile nerves was, however, variable. Changing the animal's position abolished the erectile response in three of four dogs while no change of erectile response due to anesthesia could be demonstrated in the remaining four dogs. We conclude that spinal anesthesia seems to enhance simian, but not canine, erectile response to electrostimulation of the erectile nerves, possibly via interference of the autonomic regulatory mechanism.