The molecular and crystal structure of bis(4-mercaptophenyl) sulfide (3) was determined by means of an X-ray diffraction analysis. The crystals are monoclinic, P2, /n with four molecules in the unit cell of the dimensions: a = 5,752 (I), b = 25,767 (9), c = 7,954 (2) A and / I = 95,2 (I)". The structure was solved by direct methods and refined by least-squares techniques up to R = 0,075 for 1280 independent reflections. The molecules of 3 do not have own symmetry and are arranged in the unit cell in chains along the 2, axes. Between sulfur atoms of neighbouring molecules hydrogen bonds are formed. From investigations of 3 and poly(l,4phenylene sulfide) (2) at low temperatures (down to 90 K) similarities of changes in the crystal structures of both substances were evidenced. 1 3 L 2 *) Part of this work was presented at the IX International Symposium on Organic Sulfur Chemistry, Riga 1980. 0025-1 16X/86/$03.00 z 0,6935(0) 0,7755(0) 0,561qO) 0,4781(0) 0,7328(0) 0,7750(0) 0,60(1) 0,4603(0) 0,40WO) 0,741) U 0,0886(0) 0,750(0) 0,22(5) 0,0550(0) 0,0680(0) 0,0950(0) 0,0760(0) 0,14(4) 0,0810(0) O ,~( O )