Thetransform of octahydro-1-methyl-1H-2,1-benzothiazine 2,2-dioxide, in which a six-membered sultam unit istrans-fused to cyclohexane, has been synthesized. The single-crystal X-ray structure shows the molecule to have theN-methyl group in theaxialorientation. The generalized anomeric effect believed to be responsible for the axial preference is estimated at =>2 kcal mol-1.Key words: generalized anomeric effect, negative hyperconjugation, sulfonamides, sultams, X-ray crystallography.