The hydrochloride salt form of hexaminolevulinate, a hexyl ester of the heme precursor 5-aminolevulinic acid (ALA) with potential photosensitizing activity. Hexaminolevulinate serves as a precursor of photoactive porphyrins (PAPs), particularly protoporphyrin IX (PpIX), which selectively accumulate in rapidly proliferating cells, such as those seen in tumor tissue. When exposed to blue light, PAPs are activated and emit red light thereby allowing tumor imaging.