Abstract: A novel crystalline form of the substrate known under the chemical name 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfiny] -1H-benzimidazole, and having the generic name omeprazole, hereinafter referred to as omeprozole form C, is disclosed. Further, a process for the preparation of omeprazole form C, a pharmaceutical formulation containing omeprazole form C in admixture with pharmaceutically acceptable excipients and the use of omeprazole form C for treatment of gastrointestinal disorders are disclosed.