Nucleoli are normally present in human small lymphocytes, but are not seen in the ordinary, Romanowsky-stained blood smear. They are stained easily, however, by the supravital method described in this paper, and are crisply demarcated from the adjacent chromatin. The method is simple, rapid, convenient, and applicable to any general hospital laboratory. It also stains the other leukocytes, permitting differential counts, and is useful for cytologic examination of body fluids and aspirated bone marrow. The advantages of the supravital procedure are discussed, and the relationships of nucleolar morphology and nucleolar number to various diseases are noted.