Chemosensory dysfunction is relatively common. This article describes a series of 306 patients who presented with anosmia. We divided olfactory disorders into those associated with interruption of the transport of stimulus and those associated with damage to either peripheral or central nervous system structures. Nasal and paranasal sinus disease (transport interruption) was found to be causative in 67% of patients presenting with anosmia. These patients are generally 45 years old, the loss of olfaction is progressive and associated with additional nasal symptoms. Upper respiratory infection was found to be causative in 18% of patients. They are generally older, with a mean age of 58 years and are predominantly female (78%). The loss of smell is sudden and anosmia is often accompanied by troublesome parosmias (50%). CT-scan is necessary for the evaluation of a smell dysfunction.