The dynamics of insurance agency in indonesia have fed to changes in the market structure of the life and property insurance industry in indonesia. This study examines the influence of market structure on profitability in life and property insurance companies in indonesia. Based on Concentration Ratio. this study found that from 1996-2004 the life and property insurance industry in indonesia was an oligopoly. The market structure of the life insurance industry had on average moderate concentration levels while the market structure of the property industry had on average low concentration levels. The regression model was constructed using pane! data and showed that the market structure positively influenced company profitability in both the life and property insurance industries. Yet this Positive influence was due more to efficiency than market power.