Sterols such as cholesterol (CHOL) synthesised in the endoplasmic reticulum (ER) need to be efficiently transported to the plasma membrane, where 90% of the free sterol pool resides. Conversely, sterols taken up from outside the cell need to be transported back to the ER for esterification to sterol esters. The mechanisms that control this bi-directional movement of sterols are still poorly understood but a likely candidate is protein ARV1 (ARV1). Studies with mutant yeast Arv1 indicate altered intracellular sterol distribution and subsequent defects in sphingolipid metabolism. Human ARV1, a predicted sequence ortholog of yeast Arv1, complements the defects seen associated with deletion of yeast Arv1 (Tinkelenberg et al. 2000, Swain et al. 2002).