Crystal structures are reported for five racemic 4-{3-(halophenyl)hexahydro [1,3]oxazolo[3,4-a]pyridin-1-yl}-2,8-bis(trifluoromethyl)quinolines, 2, namely (2: X ¼ 2-F, 3-Br, 4-Cl, 4-Br and 4-F), prepared from mefloquine and XC 6 H 5 CHO. In each case, the compound crystallizes in the triclinic space group, P 1 1, with Z ¼ 2. All molecules have ''F'' shapes with the X-phenyl and quinoline rings lying on one side of the best plane through the fused oxazolidine-piperidine rings. Differences in the conformations of the molecules are indicated by the differences in the interplanar angles. In each case, the supramolecular arrangements are made up from combinations of p Á Á Á p and some of C--H Á Á Á X and C--X Á Á Á p (X ¼ halo) interactions. Two similar structural sub-sets found in the crystal structures of the five derivatives are centrosymmetric p Á Á Á p-linked dimers and centrosymmetric cage-like dimers. The cage-like dimers, formed by the intermeshing of the rings of the monomers, are generated from different weak intermolecular interactions, which include C--H Á Á Á X and C--X Á Á Á p (X ¼ halo) interactions. Comparisons are made between the activities of the mefloquine-oxazolidine derivatives in in-vitro tests against the multidrug-resistant tuberculosis strain and conformations, as measured by interplanar angles.