Paraffin-embedded tissue from 38 patients with early- and advanced-stage juvenile granulosa cell tumor (JGCT) of the ovary was analyzed by flow cytometry to investigate whether the DNA content is related to the histologic features, stage, or clinical outcome. Thirty-three cases were suitable for analysis: twenty-seven Stage Ia, two Stage Ic, and four Stage III. Eighteen (55%) tumors were DNA diploid and fifteen (45%) tumors were DNA aneuploid with a mean S-phase fraction (SPF) of 13.6% and a range of DNA indices from 1.0 to 2.2. Neither the DNA ploidy nor the SPF was associated with the stage of the disease. An analysis of the relation between DNA content and histopathologic features revealed that aneuploidy was associated with high mitotic rates and to a lesser extent with high-grade nuclear atypia. DNA aneuploidy was not associated with aggressive behavior of Stage Ia JGCTs. However, among the four patients with Stage III tumors, the two with diploid, low-SPF tumors were alive and well, whereas the two with aneuploid, high-SPF tumors developed recurrences or died. These data suggest that further studies on the prognostic significance of flow cytometric analysis of DNA content in advanced-stage JGCTs are warranted.