Germany's Ifo survey of business optimism fell more than expected in August, sending another downbeat signal about Europe's largest economy.
The latest index released on Monday fell to 102.3 points in August, down from a revised 103.2 in July. Market analysts expected 102.6.
Germany's economy has done better than the rest of the eurozone, which is struggling with a crisis over too much government debt and recessions in several countries. Germany grew 0.3% in the second quarter and unemployment remains low.
But the debt crisis is having an increasing impact on Germany as growth sags among its eurozone trading partners and businesses and consumers hold off on spending and investment out of fear for the future.