In the days when Nature Biotechnology was Bio/Technology, we used to run a regular feature page entitled “Last Word.” In this issue, we resurrect this tradition, metaphorically and with profound sadness, by publishing what turns out to be the last printed words of Professor James E. Bailey. On April 28, Dr. Bailey sent us the Commentary that appears on pages 503–504. In his words, it attempts to outline “mathematical tools available that bypass the need for systems parameters and achieve strong results, including some remarks on their limitations and where we might try to go in the future.” Just 11 days later, he succumbed to metastatic cancer in the early morning of May 9, 2001 in Zurich, Switzerland. He is, and will be, deeply missed.