Breast tumor biopsies required for steroid receptor determination are normally frozen in liquid nitrogen and stored until assay. However, some limitations of this type of storage exist. To try to both eliminate the need for liquid nitrogen and as part of a study of serial assays on a single tumor biopsy, alternative storage media were investigated. This study shows that storage of breast tumor biopsies at -20 degrees in sucrose buffer made 50% in glycerol prevented the tissues from freezing, yet retained the specific estrogen receptor content both quantitatively and in terms of molecular form (8S:4S ratio). Receptor was stable for up to 100 days, and individual samples could be successfully reassayed throughout this period. Forty-four biopsies from 40 patients were halved, and one section from each was stored in liquid nitrogen, while the other was stored in sucrose:glycerol. Overall, the correlation of receptor content between the two storage methods was good. Using a clinical cutoff value of 20 fmol/mg cytosol protein, only one sample of the 44 would have been classified differently after storage in the two media. Progesterone receptor in biopsies stored in sucrose:glycerol also appears to be stable for at least a limited period.