The invention provides polymorphic crystalline forms of acid addition salts of (+)-1-(3, 4-dichlorophenyl)-3-azabicyclo[3.1.0]hexane designated as polymorph form A, polymorph form B and polymorph form C, where polymorph form A is more thermodynamically stable than the other forms, methods for preparing and using such polymorph forms and pharmaceutical compositions containing such polymorph forms.