UT-EC-2A was established from a patient with moderately differentiated Stage III endometrial adenocarcinoma with squamous metaplasia. UT-EC-2B was established from the same patient 17 months later from a metastasis in the left supraclavicular fossa. The origin of these cell lines was confirmed by DNA identity testing. Nude mice tumors produced by UT-EC-2A and UT-EC-2B cells recapitulated the histology of the original human tumors. Flow cytometric DNA contents of both primary and metastatic human tumors as well as corresponding nude mice tumors were diploid. The S-phase fractions of both cell lines were > or = 30%. The UT-EC-2A cell line was cytogenetically normal. The UT-EC-2B cell line had quite simple karyotype at low passage with an extra i(18p) and a deletion 21q, but at higher passages an additional three-way translocation 5;14;19 was observed. Radiosensitivity of the cell lines was tested with the 96-well plate clonogenic assay. The areas under the survival curves corresponding to the mean inactivation doses of UT-EC-2A and UT-EC-2B were 0.65 +/- 0.10 and 0.60 +/- 0.06 Gy, respectively. Measured survival at 2.0 Gy (SF2) was 0.042 for UT-EC-2A, 0.044 for UT-EC-2B, and 0.2 for skin fibroblasts. These cell lines are among the most radiosensitive human cancer cell lines described in the literature. Studying the characteristics of primary and metastatic cells derived from the same patient provides an opportunity to evaluate tumor progression.