This invention relates to a novel crystalline polymorph of hexyl-5-aminolevulinate hydrochloride, referred to hereinafter as Form C, which is useful as precursor of a photo sensitizer in the photodynamic diagnosis and treatment of metabolically active cells related to diseases such as cancer of the uterus, cervix, vagina, rectum, colon, lower gastrointestinal tract infection associated with cancer caused by human papilloma virus non-cancerous lower gastrointestinal tract a human inflammatory bowel disease ulcerative colitis Crohns disease inflammatory bowel syndrome dysplasia of the female reproductive system anus penis rosacea and acne and which is suitable for use as the active ingredient of a commercial pharmaceutical product. The invention relates further to methods of preparing Form C and using it in the described pharmaceutical compositions.
