This study quantitates morphologic changes seen in partial moles and hydropic abortuses in an attempt to find a correlation with DNA content. Thirty-two products of conception were studied. Fifteen were diagnosed as definitive partial moles (DPM), and 17 had changes suggestive of a partial mole (SPM). We determined DNA ploidy by flow cytometry and quantitatively analyzed the following microscopic features: villous edema and sclerosis, central cistern formation, villous blood vessels, trophoblastic proliferation, and trophoblastic inclusions. No single pathologic feature significantly correlated with DNA content, even though triploid cases showed more inclusions than diploid cases (8.3 versus 7.2 on the average per ten x 100 fields). An overall diagnosis of DPM did correlate with ploidy; 12 of 18 triploid cases (67%) compared with only three of 13 diploid cases (23%) had been previously diagnosed as DPM (p < 0.05). Flow cytometric DNA ploidy estimates DNA content and cannot determine chromosomal origin. It is possible that detailed cytogenetic studies of moles compared with abortuses may show a significant correlation of the proportion of paternal chromosomes, morphologic changes, and the risk of persistent gestational trophoblastic disease.