Male rats received bilateral olfactory bulbectomies or a sham operation at 2 days of age, 10 days of age, or in adulthood. Relative to sham-operated males, bulbectomy at 2 days of age or in adulthood reduced the proportion of males that copulated when tested as adults. In contrast, copulatory behavior was essentially normal in male rats bulbectomized at 10 days of age. The copulatory deficit in the Day-2 bulbectomized males was not a secondary effect of a testicular dysfunction because the age at preputial separation was normal and exogenous testosterone was ineffective in activating copulation in the noncopulating bulbectomized males. Neonatally bulbectomized males (both Day-2 and Day-10) showed a small, but significant, olfactory deficit when tested at 15 days of age, yet responded similarly to sham-operated males when tested in adulthood. Recovery of copulation after olfactory system damage appears to be dependent on the age of the animal at the time of the lesions. Furthermore, our results support previous suggestions that sparing of function is not a necessary consequence of the high plasticity of the developing nervous system.