A method for enhancing chemiluminescence which uses a heterocyclic compound of the formula: ##STR1## wherein R.sub.1 is an oxygen or sulfur atom or an imino group optionally substituted by 4-hydroxyphenyl, and R.sub.2, R.sub.3 and R.sub.4 are a hydrogen or halogen atom, an optionally substituted hydrocarbon residue, a heterocyclic group or the like in a luminescence system.