The role of antibodies of CD15 as diagnostic markers of Hodgkin's disease was assessed from a review of the literature. A total of 571 cases of Hodgkin's disease and 386 cases of non-Hodgkin's lymphoma were included. The sensitivity of CD15 in detecting cases of Hodgkin's disease was 80% or 91% if cases of lymphocyte predominant Hodgkin's disease were excluded. The specificity of CD15 was only 80.6%, or in other words, 19.4% of cases of non-Hodgkin's lymphoma were CD15 positive. In an ideal test both the sensitivity and specificity would be 100% and if the test performance were no better than chance then they would both be 50%. It is concluded that CD15 immunostaining cannot be regarded as a sensitive or specific marker of Hodgkin's disease. Application of this formal method of analysis to other immunohistological reagents and panels of antibodies is discussed.