Two series of [(Ln(1/3)Sr(2/3)S)(1.5)](1.15)NbS2 (1.5Q/IH) and (Ln(1-x)Sr(x)S)(1-y)NbS2 (1Q/1H) misfit layer sulfides have been synthesised and studied by X-ray powder and single crystal diffraction, EDX-analysis and magnetic measurements. For the early lanthanides (Ln = La, Cc) only the (Ln(1-x)Sr(x)S)(1+y)NbS2 (x < 0.40-0.45, y = 0.150. 17) compounds were formed whereas for late lanthanides (Ln = Pr, Nd, Sm, Gd-Er, Yb, Lu), and yttrium, both types of phases can be obtained. The crystal structure of (Pr0.55Sr0.45S)(1.15)NbS2 has been refined on the basis of X-ray single crystal data using the superspace approach. It consists of double layers [Pr0.55Sr0.45S] of NaCl-type (Q-part: a = 5.799(3) Angstrom, b = 5.810(2) Angstrom, c = 23.331(9) Angstrom, z = 4) and NbS2-sandwiches (H-part: a = 3.332(3) Angstrom), 7 = 8, yielding a q-vector q = (alpha 0 0), alpha = 0.74) alternating along the c-direction. The superspace group pair is Fm2m (alpha 0 0):Fm2m (alpha 0 0) (No. 42.7). The refinement converged to R-w(obs) = 0.069. According to the structure refinement and EDX-analysis data in the [Pr0.55Sr0.45S]-slab almost half of the Pr-atoms are randomly replaced by Sr. The minimal formal value of charge transfer from the Q- to the H-part of the structure necessary to stabilise the misfit Nb-based layer sulfides has been estimated as about 0.6 (e) over bar per Nb atom. (C) 2004 Elsevier Ltd. All rights reserved.