English Summary  
These notes are devoted to the theory of exponential sums over finite fields. The first chapter recalls some of the number-theoretic interest of such sums. The second chapter discusses the L-functions attached to such sums, the "Weil conjectures" for these L-functions as established by Deligne, and the consequences for, the exponential sums themselves. The third chapter is devoted to the cohomological interpretation of exponential sums and of their associated L-functions. These first three chapters are largely of an expository nature. The main new results are found in chapters four and five. Chapter four is devoted to theorems of unifornity "for almost all p" for the cohomological structure of quite general exponential sums. Chapter five is devoted to a precise analysis of the cohomological structure of certain specific classes of exponential sums for which the associated algebro-geometric situation is especially attractive.
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