In this study the authors have investigated the clinicopathologic correlations in 80 consecutive cases of thymoma in order to establish the clinical usefulness of histologic subtyping of these tumours. All cases were histologically examined and classified according to Salyer and Eggleston and to Marino and Müller-Hermelink classifications. Therefore, thymomas were subtyped as predominantly lymphocytic, mixed and predominantly epithelial and cortical, mixed and medullary, respectively. The frequency of the different histologic subtypes was determined, and histologic findings were related to patients' age, surgical stage, and survival. Through the application of Salyer and Eggleston classification, the three histologic subtypes did not correlate with patients' ages at time of diagnosis, surgical stage as determined by local infiltration, and prognosis as determined by survival curves. On the contrary, when Marino and Müller-Hermelink classification was applied, statistically significant relationships between histologic results and age, surgical stage, and prognosis were demonstrated. These results and their implications are discussed, with special reference to the important problem of histogenesis of thymomas and of their clinicopathologic staging.