The vortex lattice in high-temperature superconductors is affected by thermal fluctuations and quenched disorder, leading to disordered phases, such as vortex liquid and glass, through a first-order phase transition. We use a transformation proposed by Calero, in order to obtain the angular generalization of the first-order melting line of the vortex lattice in a three-dimensional anisotropic superconductor, such as YBaCuO, under an external magnetic field with arbitrary direction with respect to the anisotropy axis. The calculations are performed in the framework of the Ginzburg–Landau theory in the lowest Landau level approximation. The competition between thermal fluctuations and disorder is described following the same method as that developed by Li and Rosenstein.