Novel compounds comprising a C--C double bond substituted at one carbon with two sulfur atom-containing groups are disclosed. The compounds are useful in methods and compositions for generating chemiluminescence rapidly by reaction with a peroxidase enzyme and a peroxide. The chemiluminescence thus produced can be used as a detectable signal in assays for peroxidase enzymes or peroxide-producing enzymes and in assays employing enzyme-labeled specific binding pairs.