Abstract: The present invention relates to crystal forms of mammmalian OSC and the crystal structure information obtained from them, to methods of preparing such crystal forms, and to their use for the identification and/or design of inhibitors of OSC activity. A further subject matter of the invention are methods for the identification and/or design of inhibitor compounds of OSC activity, the inhibitor compounds of OSC activity identified by these methods and their use in pharmaceutical compositions for the treatment and/or prevention of diseases which are associated with OSC comprising hypercholesterolemia, hyperlipemia, arteriosclerosis, vascular diseases, mycoses, parasite infections and gallstones, and/or treatment and/or prophylaxis of impaired glucose tolerance, diabetes, tumors and/or hyperproliferative disorders, preferably for the treatment and/or prophylaxis of hypercholesterolemia and/or hyperlipemia.