The phase diagrams of the quasibinary systems Ag 2SP 4S 10, Cu 2SP 4S 10, Tl 2SP 4S 10 and Sb 2S 3P 4S 10 were determined by means of difference thermal and X-ray analyses. Ag 2SP 4S 10 contains the congruently melting compound Ag 7PS 6, the peritectic compounds Ag 3PS 4, Ag 4P 2S 7 and Ag 2P 2S 6 and the peritectoid high temperature compound Ag 7P 3S 11. The lattice parameters of Ag 3PS 4 and of a new high temperature modification of Ag 4P 2S 7 were determined: Ag 3PS 4, space group Pmn2 1, a=765.0(1), b=686.8(1), c=650.9(1) pm; HT-Ag 4P 2S 7, a=807.3(2), b=1102.2(3), c=636.8(2) pm, β=105.22(3)°. In the system Cu 2SP 4S 10 the congruently melting compound Cu 7PS 6, the peritectic compound Cu 3PS 4 and the new metathiophosphate (CuPS 3) n were observed. The IR and Raman spectra of the compounds are given. The systems Tl 2SP 4S 10 and Sb 2S 3P 4S 10 are simple. Similar to the system Ag 2SP 4S 10, miscibility gaps were found on the P 4S 10-rich side of these systems. The compounds Tl 3PS 4, Tl 2P 2S 6 and SbPS 4 (lattice parameters a=1306.03(5), c=627.9(5) pm) melt congruently.