Indole-3-carbinol (I3C) (2) is produced endogenously from naturally occurring glucosinolates contained in a wide variety of plant food substances including members of the family Cruciferae, and particularly members of the genus Brassica, whenever they are crushed or cooked. The acid environment of the gut very facilely converts it into a range of polyaromatic indolic compounds, e.g. (3, 4,5), which appear to be responsible for many of the physiological effects observed following the ingestion of these foods. These so-called chemopreventive compounds are important because of their enzyme induction and suppression, mutagenic, carcinogenic and, particularly, antimutagenic and anticarcinogenic properties against a variety of classes of carcinogens. These properties as well as other miscellaneous properties of these substances are critically reviewed in detail in this paper of >170 references, the second of two parts. At the present time it appears that I3C and its congeners have considerable potential as natural prophylactic anticancer agents against certain common neoplasms, especially inasmuch modern diets are increasingly deficient in these vegetable-derived substances. A short general assessment of the substantial potential of the title compounds concludes the review.