Glucosylsphingosine is the lyso-derivative of the common glycolipid glucocerebroside. Gaucher disease is characterized by an accumulation of glucocerebroside due to a deficiency in the enzyme glucocerebrosidase and it has now been found that glucosylsphingosine also accumulates in this disease.1 This accumulation of glucosylsphingosine contributes to neuronal dysfunction and destruction in patients with neuronopathic Gaucher disease2 and it has been found to be a potent inhibitor of glucocerebrosidase. At least some instances of Gaucher disease also have a deficiency in the activity of glucosylsphingosine beta-glucosidase, the enzyme responsible for cleaving off the glucose of glucosylsphingosine and glucocerebroside. Like glucocerebroside and galactocerebroside, glucosylsphingosine can increase Ca2 + mobilization from intracellular stores although it uses a different mechanism.3 Conduritol B epoxide (CBE), an inhibitor of beta-glucosidase, and l-phenyl-2- decanoylamino-3-morpholino-l-propanol (PDMP), an inhibitor of glucosylceramide synthase, can be used to create a model of Gaucher disease and consequently an accumulation of glucopsychosine.4