Pituitary hyperplasia is an uncommon condition that is difficult to diagnose, especially in small fragmented surgical specimens. Normal pituitary cells show variations in distribution, another factor complicating the identification of hyperplasis on biopsy. The process may be nodular or diffuse. It is the nodular variety that readily lends itself to histologic diagnosis. The condition affects most pituitary cell types including prolactin, growth hormone, corticotropin and thyrotropin-producing cells. Herein the authors present these various forms of piruitary hyperplasia with comments regarding their clinical presentations and the implications of making or not making a correct diagnosis.