How the brain constructs one's inner sense of gender iden-tity is poorly understood. On the other hand, the phenomenon of phantom sensations-- the feeling of still having a body-part after amputation--has been much studied. Around 60% of men experience a phantom penis post-penectomy. As transsexuals report a mismatch between their inner gender identity and that of their body, we won-dered what could be learnt from this regarding innate gender-specific body image. We surveyed male-to-female transsexuals regarding the incidence of phantoms post-gender (...) reassignment surgery. Addition-ally, we asked female-to-male transsexuals if they had ever had the sensation of having a penis when there was not one physically there. In post-operative male-to-female transsexuals the incidence of phan-tom penises was significantly reduced at 30%. Remarkably, over 60% of female-to-male transsexuals also reported phantom penises. We explain the absence/presence of phantoms here by postulating a mis-match between the brain's hardwired gender-specific body image and the external somatic gender. Further studies along these lines may provide penetrating insights into the question of how nature and nur-ture interact to produce our brain-based body image. (shrink)