We investigate the effects of employee share ownership (ESO) on three alternative measures of firm performance in a panel of 1,115 companies from the five largest European economies. The results show that firms with ESO enjoy significantly higher levels of capital market performance and of accounting performance than firms without ESO; however, the marginal effects of ESO are declining with increasing ESO levels. ESO does not have a clear effect on productivity. These findings hold for all countries except Spain. Variations in ESO levels within firms over time exert few performance effects.