Despite the fact that immunohistochemistry is widely used in routine diagnostic work and is a very common part of scientific reports in pathology and cytology, its standardization still lags behind. Interpretation of immunostains should be based on microanatomic distribution of the staining, proportion of positively stained cells, staining intensity, if relevant, and cutoff levels. These parameters should be shown to be reasonably reproducible and should be clearly defined in publications. Uniformity in the setting of thresholds could probably benefit from interlaboratory control materials containing defined amounts of the target antigen. Reliable and precise quantitative immunohistochemistry requires the use of control materials containing defined amounts of the target antigen and processed alongside the specimen combined with automated computer-assisted microspectrophotometry. Application of these suggestions is hoped to improve standardization and to facilitate communication in the field of immunohistochemistry.