Abnormal nuclear DNA content, as determined by flow cytometry, when combined with conventional prognostic variables such as tumor grade or stage at diagnosis, appears to identify patients who are at increased risk for recurrence of disease. The DNA content of ovarian dysgerminoma, a tumor that is homologous to testicular seminoma and is found in young women of childbearing age, was studied to determine if there is a correlation between DNA content and outcome. Such information would be useful in selecting treatment regimens and making possible the preservation of childbearing potential in women who are likely to have a good outcome. The specimens from 23 cases of ovarian dysgerminoma seen at our institution between 1950 and 1985 were analyzed by DNA flow cytometry. Five of the tumors were diploid (21%) and nineteen were nondiploid (79%). Patient outcome was not predicted any better by nuclear DNA content than by conventional prognostic variables.