Four liquid crystalline compounds, i.e., three terephthal-bis-4-n-alkylanilines (TBAA; alkyl = pentyl, hexyl, and heptyl) andN-(4-n-heptyloxybenzylidene)-4-n-hexylaniline (HBHA) were synthesized and the phase transitions were studied by means of optical microscope, differential scanning calorimeter and miscibility relationships. It is indicated that all the compounds exhibit a smectic B-smectic B phase transition of which the transition heat is very small. Furthermore, a brief description is given of a smectic phase of TBAA which occurs only monotropically.