Three-hundred and sixty-six patients affected with seminoma testis (234 stage I, 85 stage II low, 47 advanced diseases) were treated between January 1968 and December 1985. Overall incidence of anaplastic lesions (43 patients) was 12%, progressively increasing with stage of the disease (9% stage I, 13% stage II low, 21% advanced disease). Only 343 patients submitted to exclusive curative/prophylactic radiotherapy were studied: 35 of them were anaplastic (22 stage I, 11 stage II low, 2 advanced disease). Radiation therapy was always performed regardless of the histologic subtype. Recurrences occurred in 14% of anaplastic tumors (5/35) and in 7.5% of classical seminomas (23/308). There was no statistically-significant difference between global and stage-by-stage failures. After literature review and complete analysis of the patterns of recurrence, the authors stress the lack of evidence suggesting a different radioresponsiveness of anaplastic versus classical seminomas; nonetheless, a more accurate staging is recommended for anaplastic variants, since they tend to appear in the advanced stages of the disease.