In this work is described the thermodynamic properties and structural data of the homologous series 3-5 (4-alkoxyphenyl)5(2-propylthienyl) and 3-5(4-alkoxyphenyl)5(2-hexylthienyl) -pyrazoles and -isoxazoles. The series isoxazoles exhibit nematic phases and compounds with greater number of carbon atoms in the alkoxy chains also exhibit the smectic C phase. In contrast, the pyrazoles series exhibit only the smectic A phase.