The present invention relates to a novel form of the (-)-enantiomer of 5-methoxy-2-[[(4-methoxy-3,5-dimethy1-2-pyridinyl)-methy1]sulfiny1]-1H-benzimidazole, i.e. S-omeprazole. More specifically, it relates to a novel form of the magnesium salt of the S-enantiomer of omeprazole trihydrate. The present invention also relates to processes for preparing such a form of the magnesium salt of S-omeprazole and pharmaceutical compositions containing it. Furthermore, the present invention also relates to new intermediates used in the process. 0 S-151 85 Sodertalje, Sweden. ASTRA AKTIEBOLAG 1344/DEL/1998 1344/DEL/1998 INDIA 2009-03-25T18:00:34Z 2005-03-04 1998-05-20 411467 1) HANNA COTTON 2) ANDERS KRONSTROM 3) ANDERS MATTSON 4) EVA MOLLER -2 0 3236 2005-03-04 0 2DM5cU3K 2009-04-30T18:54:53Z 127968 1) HANNA COTTON 2) ANDERS KRONSTROM 3) ANDERS MATTSON 4) EVA MOLLER 11814 ASTRA AKTIEBOLAG