Several longitudinal studies show that over time the American public has become more approving of euthanasia and suicide for terminally ill persons. Yet, these previous findings are limited because they derive from biased estimates of disaggregated hierarchical data. Using insights from life course sociological theory and recently developed cross-classified mixed effects logistic regression, I better account for this liberalization process by disentangling the age, period, and cohort effects that contribute to longitudinal changes in these attitudes. Findings indicate that while attitudes toward euthanasia and suicide have liberalized over time, they remained relatively stable over the past 10 years. Furthermore, this study finds significant age effects in which the probability of agreement to euthanasia and suicide steadily decreases throughout the life course. Contrary to previous research, this study finds that when controlling for age and period effects, there are no significant birth-cohort effects that contribute to longitudinal changes in these attitudes.