Disclosed is an apparatus and a method for surgical dilation and retraction of tissues during a medical procedure, for example a spinal surgery. The apparatus includes a dilator assembly that includes a plurality of slidingly engaging dilators, wherein at least one dilator includes an outer wall shape different from its inner wall shape. At least one of the dilators may include an eccentrically positioned circular channel, a generally oblong outer wall shape, and a longitudinal gap in a wall. The dilator system may be used in a method that provides off center differential dilation of tissues in one or more preferred directions. A retractor system that may be used with the dilator system is also disclosed.
