In 1996 free choice of health insurers has been introduced in the German social health insurance scheme. Competition between insurers was supposed to increase efficiency. A crucial precondition for effective competition among health insurers is that consumers search for lower-priced health insurers.We test this hypothesis by estimating the price elasticities of insurers? market shares. We use unique panel data and specify a dynamic panel model to explain changes in market shares. Estimation results suggest that short-run price elasticities are smaller than previously found by other studies. In the long-run, however, estimation results suggest substantial price effects.