Studies on organized crime face numerous methodological problems because these criminal activities are concealed from the public and most information comes from indirect sources. The researcher usually relies on government data which is based on news items, criminal informants, and wiretapping and bugging. However, newspapers do not always document their stories and may use government sources themselves, while organized criminals' custom forbids mentioning any specific dates, names, or places in most conversations. Furthermore, persons in organized crime tend to exaggerate their importance to impress friends and colleagues. Other researchers have become marginal participants in closed societies, but the reliability of data obtained in this manner is questionable. A trusting relationship is difficult to establish without the observer actually participating in illegal activities, in which case the researchers begin to influence the events they are supposedly investigating. Reviews of Francis Ianni's study of the Mafia and John Landesco's work on organized crime in Chicago during the 1920's demonstrate these problems. A life history approach is suggested which describes all important events in a person's life that can be documented. Although material on a subject may be limited, several life histories together can provide a more accurate picture of organized crime. The article contains 5 footnotes and 20 references.