An essential issue for laboratory experiments to inform policy debates is the "external validity" of the experimental results; that is, does behavior in the laboratory apply to behavior that occurs in the naturally occurring world? We examine this issue of external validity in the specific context of laboratory experiments on tax compliance, using two different types of evidence. We find that the behavioral patterns of subjects in the laboratory conform to those of individuals making a similar decision in naturally occurring settings. We also find that the behavioral responses of students are largely the same as those of nonstudents in identical experiments. (JEL C9, H0, H3)