To use as substrate/chromogen in conjunction with peroxidase based immunostaining systems. Note: The working chromogen solution is stable for 6 hours. Any solution not used after this period should be discarded. 1. Take 5 ml of distilled or de-ionized water in a test tube. 2. Add two drops of concentrated buffer and mix. 3. Add two drops of concentrated AEC cromogen and mix. 4. Add two drops of 3% H2O2 substrate solution and mix. Procedure: 1. Once tissue sections have been incubated with peroxidase, wash them with buffer thoroughly. 2. Wipe the class to remove excess buffer and add enough drops of the working AEC solution to cover the tissue sections. 3. Incubate for 10-20 mintues at room temperature. For the best results, look under the microscope for the signal development. Once desired signal to noise ratio is achieved, stop the reaction by washing slides in wash butter.