Sex does matter. One of the most compelling reasons for understanding the biological differences, which are not so explained at this time, is that there are striking differences in human disease. The most obvious and best-studied differences between the sexes are in the reproductive systems. Much less study has been done on sex differences in non-reproductive areas of biology. Liver cancer is undoubtedly predominant in men and postmenopausal women. Almost anyone may "feel," but not recognise the sex-associated difference in liver cancer as a fact. How does sex matter in the incidence of liver cancer? After considering the data and examples presented in this book, anyone will be provided unique opportunities to obtain a better understanding of differences of chronic liver disease between the sexes. Some of these differences can be explained by what we now know. Some are unexplained and point to important questions for future study. Being female or male is an important basic human variable that affects health and liver disease throughout the life span. A better understanding the biological mechanisms underlying the sex-associated differences in chronic liver disease would provide valuable information to design care of health and liver disease more effectively for individuals, both females and males.