A chemiluminescent assay method and compositions are described which use a haloalkoxy group-substituted dioxetane which is deprotected by a hydrolytic enzyme to undergo a chemiluminescent reaction. Chemiluminescent 1,2-dioxetane compounds substituted on the dioxetane ring with a haloalkoxy group which can be triggered by a reagent to generate light are disclosed. Haloalkoxy group-substituted dioxetanes are useful for the detection of triggering agents including enzymes. The enzyme may be present alone or linked to a member of a specific binding pair in an immunoassay, DNA probe assay or other assay where the enzyme is bound to a reporter molecule.