X-ray reference powder patterns and crystal structures have been determined for a series of titanium- and cobalt-containing layered alkaline-earth compounds with nominal formula (BaxSr1-x)Ti6Co6O19 (x=0.2, 0.4, 0.6, 0.8). Structural isomorphism of the title compounds with the hexagonal ferrite BaFe12O19 and magnetoplumbite (PbFe12O19), was confirmed. The (BaxSr1-x)Ti6Co6O19 series crystallize in the space group of P63/mmc (No. 194) and Z=2. The lattice parameters range from a = 5.90729(6) Å, c = 23.2378(3) Å, and V = 702.27(2) Å3 for x=0.2 to a = 5.91493(9), c = 23.3391(5) Å, and V = 707.15(2) Å3 with x=0.8. The structure consists of alternating spinel S-block and R-blocks. The tetrahedral sites within the spinel S-blocks are occupied with only Co2+, while Ti4+ is mainly located in the octahedral sites of the spinel S-blocks and in the face-sharing octahedral site of the R-blocks. A bipyramidal mixed Co/Ti site was confirmed in the R-block of the structure. Powder X-ray diffraction patterns of this series of compounds have been submitted to be included in the Powder Diffraction File (PDF).