We compared the DNA content (DI) by cell image analysis with the karyotype and morphological phenotype of paraffin-embedded tissues from 51 spontaneous abortions. The study included 21 cases with triploid, 19 cases with diploid, and 11 cases with aneuploid (monosomic, trisomic, or mosaic) karyotype. Measurements were performed by image analysis on the trophoblastic and stromal cells of chorionic villi using 5-microm-thick, Feulgen-stained sections. At least 200 cells were analyzed. Results were interpreted using DI ranges of 1.3 to 1.7 for triploid and 0.9 to 1.1 for a diploid profile. All 21 cases with a cytogenetically confirmed triploid karyotype had DI values within the triploid range, and all 19 cases with a diploid karyotype had DI values within the diploid range. All of the trisomies and monosomies also had a DNA mass within the diploid range. However, eight cases with a triploid karyotype also had a peak in the diploid range: one case with a diploid karyotype and one case with a trisomic karyotype each had an additional peak in the triploid range. We did not find a morphological correlation either with image analysis or with karyotype. We conclude that cell image analysis is a reliable method for detection of triploidy in spontaneous abortions. This relatively rapid method allows visual discrimination of the areas to be analyzed, avoids the problem of maternal cell contamination, and may unmask mosaic karyotypes that would go unrecognized by cytogenetic studies alone.