Financial stability has become an important topic, especially in recent years. However, there is no consistent approach for measuring the financial stability of insurance companies. The aim of this paper is to assess the financial stability of insurance companies in the Czech insurance market using the financial stability summary index. We construct and applied the financial stability index separately for insurance companies that predominantly provide life insurance and non-life insurance. The financial stability index focuses on five areas. The results show that insurance companies specialised in a particular non-life insurance product are more financially stable. The research suggests that the evolution of insurance companies has been influenced by organisational changes and economic changes. During the period 2004-2019, the examined insurance companies did not show any problems in terms of financial stability.