Let Kl(a,b;n) be
the usual Kloosterman sum modulo n, with coefficients a and b. We give
upper and lower bounds for the sum ∑n≤x|Kl(1,1;n)|∕, and for related
sums, by using large sieve techniques and Deligne-Katz theory of exponential
sums. Extensions to more general exponential sums of dimension one are also
given.