The cytogenetic findings in 31 liposarcomas from 26 patients are reported. Four other tumors did not grow. Three histologic types are represented in this analysis. The well-differentiated liposarcomas were characterized by telomeric associations, large marker chromosomes and ring chromosomes, and in some cases, double minutes. The pleomorphic liposarcomas contained very high clonal chromosomal numbers with near-tetraploid modes and numerous variable, often unidentifiable, chromosomal abnormalities. The myxoid liposarcomas were characterized primarily by a t(12;16)(q13;p11) as the sole abnormality or additional changes. These results indicate that cytogenetic findings may provide a new criterion, not only for establishing the diagnosis of liposarcoma, but also for differentiating confusing histologic types of liposarcoma and these lesions from other types of sarcomas.