TWO YEARS AGO I assembled a Forum in this Journal that was consecrated to the field of heme oxygenase (HO). Since then, the phenomenal rate of expansion of the field, which extends its reach into the very core of many systems, justifies this re-visitation. In this time span, over 1,300 articles have been published that directly or indirectly refer to the HO system and heme degradation products. The majority of this new information extends the topics that were addressed in the Forum including regulation of HO-1 gene expression (5, 18, 81, 84), antioxidant activity of bile pigments (8, 73), and the function of the HO system as a key component of cytoprotection against oxidative stress and free radicalmediated insult in various tissues—the brain (45, 66), kidneys (80), and the heart (54). Clearly, it would not be feasible to acknowledge the vast majority of the scholarly contributions that have been made to those topics in the past 2 years; a small minority is selected for this visitation. First, however, a brief introduction to the basics of the system is provided.