Key Points- Congenital anosmia is usually associated with Kallmann syndrome, which is characterized by hormonal abnormalities such as hypogonadotropic hypogonadism.- On very rare occasions, an isolated congenital anosmia presents as olfactory bulb agenesis without this associated syndrome.- In previous studies of such cases, diagnosis is usually based on the absence of an olfactory bulb on structural MRI, rather than on objective functional measures.- Simultaneous functional MRI and olfactory event-related potential recordings can provide highly objective evidence of olfactory function.- We examined both structural and functional MRI and olfactory event-related potential data to diagnose isolated congenital olfactory bulb agenesis, gaining objective evidence of olfactory function.