Many methodologies exist to perform an immunoenzyme double staining. Hence, the practical problem arises as to which of these methods is optimal for one's own experimental design. A process of selection is described which is derived from our own practical experience. First, a general strategy is outlined for the handling of tissue sections to be used for multiple staining methods. Secondly, the selection of an appropriate immunoenzyme double-staining concept is made using a flow chart. Thereafter we give criteria for the definitive selection of an immunoenzyme double-staining protocol based on the characteristics of the tissue or cell type under study. Particular attention is given to the selection of appropriate detection systems, applying enzymes or gold particles, and good contrasting colour combinations. The problems of visualizing co-localization using immunoenzyme double staining are dealt with, and suggestions are made to adapt the method, if necessary, in order to optimize it.