Immunohistochemistry of Estrogen Receptor (ER) and Progesterone Receptor (PR) has been performed in 687 cases of human breast cancer. The staining results have been compared by (1) computer-assisted image analysis (QIC Score) and (2) subjective grading of the cryostat sections ("German" IRS). Tumors without or with only weak ER or PR content may be distinguished by both methods from tumors with a high receptor content. The QIC Score values belonging to the intermediate IRS grades are distributed over a wide range, but no negative cases were found in these categories. It is concluded from our results that subjective grading of the slides is a simple, rapid and useful method for the determination of the tissue receptor content and must not be replaced by the expensive and time-consuming computer-assisted image analysis in daily practice.