The DNA content of epithelial cell nuclei of 9 cases of intermediate papillary mucinous cystomas of the ovary was determined by microspectrophotometric measurements of Feulgen-stained sections. Two cases of histologically benign and 3 cases of malignant mucinous cystomas were also measured. A diploid to tetraploid DNA distribution was found in each case of mucinous cystadenoma (MCA). The 3 cases of mucinous cystadenocarcinoma had an aneuploid DNA distribution. Three of 9 intermediate papillary mucinous cystomas had an aneuploid DNA pattern whereas in the remainder of that group the distribution was within the diploid to tetraploid range.