Abstract Two crystal forms 1 and 2 were found for the title compound. DSC measurements showed that the two crystals transform to different mesophases (Sm* I and Sm* J). Crystal data. 4′-Heptyloxy-4-biphenylyl p-[(S)-2-methylbutyl]benzoate, 1, Mr=458.61, C31H38O3, monoclinic, P21, T=298 K, a=15.065(3), b=45.59(2), c=5.636(1) Å, β=95.51(2)°, V=4109(2) Å3, Z=6, dx=1.118 Mg m−3, μ=0.475 mm−1, F(000)=1488; 2, triclinic, P1, a=13.37(2), b=22.96(2), c=10.213(5) Å, α=105.55(5), β=105.22(6), γ=102.31(9)°, V=2775(5) Å3, Z=4, dx=1.102 M gm−3. The crystal structure of 1 has been determined by single crystal X-ray analysis. Final R was 0.109. The crystal has a distinct layer structure similar to that of a smectic liquid crystal. Two of the three crystallographically independent molecules with extended paraffin chains have parallel arrangement, to which the third molecule with a twisted and highly disordered chain is antiparallel. The paraffin chains of the parallel molecules in a layer have close contacts with each other. Such contacts would enhance the intra-layer interaction which causes the transition to Sm* I.