It is my pleasure to introduce you to my special issue on “New Directions in Research Examining Crime over the Life-Course.” The overall goal and purpose of this special issue is to disseminate theoretically grounded and empirically sound research that investigates the complex nature of studying crime over the life-course going beyond merely stating that prior offending is related to future offending. The series of high-quality articles included in this special issue are from diverse methodological approaches and utilize advanced statistical techniques and longitudinal data to explore offending over various developmental periods of the life-course. Before discussing the contribution of each article, it is necessary for me to emphasize why longitudinal research is particularly important for our discipline. Longitudinal research in its most basic form (as applied to the study of crime), involves the identification of a cohort at birth and following that group of individuals throughout their life, or at least long enough to capture the termination of the majority of criminal careers (Blumstein et al. 1986, p. 104). The longitudinal method allows for a specified cohort’s level of involvement in crime to be traced as the cohort, itself, matures (Greenberg 1985). This knowledge is crucial for detecting causal factors or sequences that associate individual characteristics or certain events to consequential offending (Blumstein et al. 1988). Longitudinal data also permits the use of complex behavioral models because they allow one to examine the effects of missing or unobserved variables that may be correlated with crime (i.e., also known as the unobserved heterogeneity problem). It is often the case that even among people who have similar characteristics (race, age, sex) there is a substantial amount of heterogeneity. Thus, it is important to Am J Crim Just (2010) 35:87–92 DOI 10.1007/s12103-010-9077-z