Making a good epidemiological study requires many things, which I have spent the last five years learning about. When the results are finally ready to reach the public eye, they have to be illustrated in an honest and transparent way, laying all the cards on the table, while admitting the flaws that are always present in each and every study. Perhaps by practicing the same kinds of methods in personal life (i.e. being honest and admitting the flaws) could make every person a better person. The participants in this book consist of Icelandic men born in the early 20th century originating from a small, relatively isolated population with very distinct dietary habits. The data from this book suggest that rye bread, milk, salted or smoked fish and fish oil consumed in adolescence and/or older ages affect prostate cancer risk.