A new approach to Mourre’s commutator theory is developed. Let \(H\) be a selfadjoint operator in a Hilbert space \({\mathfrak H}\). Let \(\tau\in C_c^\infty (\mathbb{R})\) and set \(H_\tau=H\tau(H)\). The limiting absorption principle (LAP) for \(H_\tau\) implies that for \(H\). That means, the strict Mourre estimate for \(H_\tau\) implies the LAP for \(H\). The authors also show the LAP for the reduced resolvent and study the regularity of eigenvectors of \(H\). An example is constructed where the reduced LAP holds but the original Mourre estimate does not.