Further developments of an immunoenzymatic slide technique to demonstrate cell surface antigens with monoclonal antibodies are described. In this method cells are attached to polylysine coated glass slides in order to facilitate the handling of low cell numbers and to save antibodies and time for washing the cells. The technique has been modified for the labelling of viable cells. Endogenous peroxidase is used as an additional cell marker which does not interfere with the demonstration of antigens on the cell surface by immunoperoxidase methods. Damaged cells can be identified reliably, thereby minimising interpretation errors due to non-specific antibody uptake. A double labelling technique employing peroxidase and alkaline phosphatase coupled reagents is presented. Results of this slide technique are clear cut, so that evaluation can be performed by trained technicians.