Various growth media and procedures for tissue disaggregation and culturing were tested with regard to cell attachment, the type of cells to grow out, and the emergence of cytogenetically abnormal clones in cultures of 20 primary breast carcinomas. Clonal chromosome abnormalities were detected in 16 cases (80%). Our findings allow us to suggest a series of modifications of existing culturing and chromosome preparation techniques for breast cancer cytogenetic analysis. The improvements include: (1) combined mechanical and enzymatic disaggregation of the tumor samples, (2) initiation of short-term cultures in plastic flasks that have a Primaria-modified tissue culture surface or have been coated with Vitrogen 100, (3) use of serum-free growth medium, CDM-5, but with temporary (24 hours) enrichment with 20% FBS if rapid cell attachment is not achieved, (4) partial and sequential harvesting of the cultures, and (5) use of minimal volumes of hypotonic and fixative solutions during harvesting.