Bicomponent mixtures of 4-cyanobiphenyl-4′-yl 4′-alkylbiphenyl-4-carboxylates (nCBB) and 4-alkoxy-4′-cyanobiphenyls (nOCB) were studied and their phase diagrams obtained by thermomicroscopy. The strong enhancement of a smectic Adphase in mixtures with the smectic members of thenOCB (n⩾ 8) series and the induction of a smectic Adphase in the shape of an island surrounded by a nematic phase in mixtures with the nematic members of thenOCB (n< 8) series were observed. The influence of aliphatic chain length on the observed phenomena is discussed.