The invention concerns novel, pharmaceutically useful 1,3-dioxane alkanoic and alkenoic acid derivatives of the formula I in which the groups at positions 2, 4 and 5 of the 1,3-dioxane ring have cis-relative stereochemistry, Y is ethylene or vinylene, n is 1-4, Z is hydrogen or hydroxy, and X is a pyridine containing group (as defined hereinafter); and the pharmaceutically acceptable salts thereof. The invention also includes processes for the manufacture and use of the acid derivatives as well as pharmaceutical compositions for therapeutic use in one or more of a variety of diseases such as ischaemic heart disease, cerebrovascular disease, asthmatic disease and/or inflammatory disease.