In the paper three kinds of framework of strain gradient plasticity recently developed and their applications are reviewed: strain gradient plasticity for CS solid-the couple stress-theory, strain gradient plasticity for SG solid, and mechanism-based strain gradient (MSG) plasticity. The applications are mainly focussed on the fracture problems. One way of accounting for material compressibility is suggested. The review is confined to the deformation theory version, though the flow theory version can be parallelly constructed.