Experimental studies on the two solid solutions franckeite s.s. and cylindrite s.s. yielded among others thePb-free endmembers of franckeite and cylindrite respectively. In these endmembers the lead content of the twomineral phases are completely substituted by bivalent tin. A third phase, ottemannite s.s. with (Fe. Sb)-bearingcompositions, was further identified in the Pb-free 4-component system Fe-Sn-Sb-S. Pb-free franckeite andcylindrite could only be synthesized as homogeneous phases at high temperatures. The ottemannite s.s. was ob-tained at 600℃ but an extensive existing range was also confirmed at temperatures below 500℃. The phase relations were discussed in the pseudoternary subsystem SnS-SnS_2-FeSb_2S_4. The following se-quence of Pb-free phases and phase assemblages were observed under increasing Sn~(4+) content at 600℃:herzenhergite (SnS)+franckeite, franckeite, franckeite+cylindrite, cylindrite, cylindrite+(Fe, Sb)-ottemannite.(Fe, Sb)-ottemannite. (Fe. Sb)-ottemannite+berndtite (SnS_2). The assemblage cylindrite+berndtite was identi-fied in synthetic systems involving Pb. The phase Fe. Sb-ottemannite s.s. appears to be stable only under Pb-de-ficient and high sulfur fugacity conditions.