Anionic polymerization of styrene using sec-BuLi as an initiator was conducted in a microflow system. A high level of molecular-weight distribution control was achieved under easily accessible conditions, such as at 0 degrees C (M-w/M-n = 1.08) and 24 degrees C (M-w/M-n = 1.10). The polymerization of styrene derivatives having silyl, methoxy, silyloxy, alkynyl, and alkylthio groups on the benzene ring also took place in a highly controlled manner using sec-BuLi as an initiator. The end functionalization using chlorosilanes and block copolymerization were also achieved in microflow systems. The end functionalization with dichlorodimethylsilane led to the formation of a chlorosilane having a single polymer chain on silicon. The subsequent reaction with another active polymer chain gave block copolymers having two different polymer chains on a silicon core.