These volumes represent the "state-of-the-art" in morphological methods for detection of steroid receptors. Some physician authors have applied many of the new methodologies in clinical research projects deisgned to improve medical practice, and these attempts have been placed in Volume II. The Background and recent advances presented here are intended to stimulate further experimentation and new innovations, and spur clinical trials by all investigators with an interest in steroid hormones, cell biology, and clinical oncology.