We analyze effects of public debt in a basic endogenous growth model with productive public spending. We demonstrate that a discretionary policy violates the inter-temporal government budget constraint along a balanced growth path. A balanced government budget gives a unique saddle point stable growth path. With a rule based policy, two saddle point stable balanced growth paths can occur, depending on the inter-temporal elasticity of substitution of consumption and on the primary surplus policy. Higher debt goes along with smaller long-run growth and we derive a condition such that a deficit financed increase in public spending raises the growth rate.