The vortex solid-vortex liquid transition, i. e., the vortex lattice (vortex glass) melting line, Hm(T) (Hg(T)) is the most heavily studied phase boundary in the H-T phase diagram of type-II superconductors. Debate has continued for many decades as to the nature of the transition and of the vortices themselves. The vortex glass melting transition has been investigated in the type -II superconducting compounds YBa₂Cu₃O7-delta, YBa₂Cu₃O₆.₅ , Y(1-x)Pr(x)Ba₂Cu₃O₆.₉₇, MgB₂, and CeRu₂. By performing measurements of magnetoresistivity, rho(H, T), voltage- current V-I , and magnetization, M(H,T), and by analyzing the behavior in the region of the melting transition, physical properties of the host materials and how these contribute to the nature of the melting transition have been revealed