Hours constraints are typically identified by worker responses to questions asking whether they would prefer a job with more hours and more pay or fewer hours and less pay. Because jobs with different hours but the same rate of pay may be infeasible when there are fixed costs of employment or mandatory overtime premia, the constraint in those cases may be illusory. Cross-section estimates of reported hours constraints are consistent with this model implying that the overall level of hours constraints may exaggerate the extent to which the labor market is characterized by frictions and imperfections. (Contains 10 tables, 2 figures, and 11 footnotes.)