A route to well-defined side-chain liquid-crystalline polysiloxanes (ratio of weight- to number-average molar masses (M) over bar(W)/(M) over bar(n) < 1.2 is reported. Anionic ring-opening polymerization of pentamethylvinylcyclotrisiloxane yielded a poly(dimethylsiloxane-co-methylvinylsiloxane) backbone. A flexible disiloxane spacer was used to connect 4-(omega-alkenyloxy)-4'-cyanobiphenyl mesogenic molecules to the vinyl groups which belong to the backbone, leading to a side-chain liquid-crystalline polysiloxane (SCLCP) which has its mesogens distributed regularly along the main chain. Preliminary measurements indicate an electro-optic switching time tau(s) = 1 min at 20 degrees C and 7 s at 32 degrees C (dc, 5 V/mu m).