Four Ewing's sarcomas were examined for chromosomal characteristics, growth in cell culture, tumorigenicity in nude mice, and presence of beta-adrenergic receptors. Three tumors were from untreated patients (one obtained directly from the patient and two after growth in nude mice) and one was a metastatic lesion obtained after treatment. All four tumors were diploid or near-diploid, with one or more structural rearrangements. In the metastatic lesion, 21 abnormalities were seen. No specific chromosome aberration was found to be common to all four tumors, although a t(1,16) was observed in two and a t(11;22) in two. Abnormalities involving chromosomes #1, #3, #11, #13, #16, and #22 were each found in two of four tumors. All four tumors were tumorigenic in nude mice; two grew well in cell culture, one of which became an established line, and all four expressed high concentrations of beta-adrenergic receptors.