Book excerpt: We study the long-run relationship between public debt and growth in a large panel of countries. Our analysis takes particular note of theoretical arguments and data considerations in modeling the debt-growth relationship as heterogeneous across countries. We investigate the issue of nonlinearities (debt thresholds) in both the cross-country and within-country dimensions, employing novel methods and diagnostics from the time-series literature adapted for use in the panel. We find some support for a nonlinear relationship between debt and long-run growth across countries, but no evidence for common debt thresholds within countries over time.