Abstract: The large electric fields of high-intensity lasers make it possible to accelerate charged particles in much shorter distances than the conventional accelerators are capable of, leading to compact sources of energetic electrons or ions. Efficient acceleration of charged particles by such lasers fields has been an important challenge over the past years. Mechanisms of vacuum acceleration use a direct interaction of strong laser fields to accelerate the particles, and because of its experimental simplicity has some advantages over the laser-plasma accelerators. The mechanisms are also based on single-particle theory and simulation. In this presentation, we talk about the basics and difficulties of this research field briefly, and then discuss some novel mechanisms that we have proposed for efficient acceleration of charged particles in vacuum.