We have studied the presence of aneuploidy and S phase in specimens containing gastrinomas from patients with Zollinger-Ellison syndrome. All patients with multiple stem line aneuploidy had widespread disease while all patients with a single aneuploid population had localized disease. The correlation between disease and ploidy was significant with P=0.00022. Our findings also suggest that ploidy may be of prognostic importance in patient survival; however, a longer follow-up time and greater number of patients is necessary to determine if this is significant. High S-phase correlated significantly with widespread disease (P=0.0039). Therefore, DNA content analysis of gastrinomas provides important information that can be utilized by the clinicians in treatment decisions. More aggressive therapy in patients with multiple stem line aneuploidy or high S-phase may prevent metastases and widespread disease. We are studying the DNA content of thyroid carcinomas from children and adults in the region contaminated with radiation from the Cherynobl accident, adults in the United States with a history of radiation exposure, and American adults with no history of radiation exposure. We will study the correlation between a history of radiation exposure and the incidence of aneuploidy as well as S phase in thyroid carcinoma. The prognostic value of DNA content analysis in these tumors will be evaluated. This information may also be useful in early detection of thyroid carcinoma in patients at high risk for this disease due to radiation exposure from occupational or therapeutic sources. We are completing a study on the prognostic value of DNA content analysis in a group of lymph node negative breast carcinomas. This is a controversial area of research with many studies complicated by differences in the population studied and treatment received. Our patients are a homogeneous population from Argentina that have all been treated by the same clinician. This test is currently being used by oncologists in evaluation of breast cancer for adjuvant chemotherapy to prevent metastatic disease. Further study is necessary to clarify the prognostic value of this test.