The invention relates to novel crystalline forms of (2R)-2-[(R)-(2-ethoxyphenoxy)-phenylmethyl]morpholine hydrochloride. In various embodiments, the novel crystalline forms may be substantially enantiopure. The preparation and characterization of the novel crystalline forms of (2R)-2-[(R)-(2-ethoxyphenoxy)-phenylmethyl]morpholine hydrochloride is also described. The invention also relates to pharmaceutical compositions containing novel crystalline forms of (2R)-2-[(R)-(2-ethoxyphenoxy)-phenylmethyl]morpholine hydrochloride, which are useful to treat and/or prevent various conditions such as nervous system and pain disorders.