A novel mixed salt of S-[2-[(1-Iminoethyl)amino]ethyl]-2-methyl-L-cysteine is disclosed. The novel mixed salt, S-[2-[(1-Iminoethyl)amino]ethyl]-2-methyl-L-cysteine maleate hydrochloride, may be produced to form crystals that may be arranged as generally orderly packed agglomerates, which are particularly useful in making pharmaceutical compositions. Such pharmaceutical compositions are also described, as well as methods to make crystalline S-[2-[(1-Iminoethyl)amino]ethyl]-2-methyl-L-cysteine maleate hydrochloride, and methods of treating conditions characterized by an overexpression on nitric oxide from the inducible isoform of nitric oxide synthase using the S-[2-[(1-Iminoethyl)amino]ethyl]-2-methyl-L-cysteine maleate hydrochloride.